ACM Research (ACMR) 10-Q 8 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2021shares
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Document Transition Report	false
Entity File Number	001-38273
Entity Registrant Name	ACM Research, Inc.
Entity Central Index Key	0001680062
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-3290283
Entity Address, Address Line One	42307 Osgood Road, Suite I
Entity Address, City or Town	Fremont
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94539
City Area Code	510
Local Phone Number	445-3700
Title of 12(b) Security	Class A Common Stock, $0.0001 par value
Trading Symbol	ACMR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Class A Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	17,811,907
Class B Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	1,695,938

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 65,036	$ 71,766
Trading securities (note 16)	30,219	28,239
Accounts receivable, less allowance for doubtful accounts of $0 as of September 30, 2021 and December 31, 2020 (note 4)	84,787	56,441
Other receivables	13,165	9,679
Inventories (note 5)	176,609	88,639
Prepaid expenses	7,531	5,892
Total current assets	377,347	260,656
Property, plant and equipment, net (note 6)	10,005	8,192
Land use right, net (note 7)	9,556	9,646
Operating lease right-of-use assets, net (note 11)	4,599	4,297
Intangible assets, net	556	554
Deferred tax assets (note 21)	15,795	11,076
Long-term investments (note 14)	7,408	6,340
Other long-term assets (note 8)	44,243	40,496
Total assets	469,509	341,257
Current liabilities:
Short-term borrowings (note 9)	15,201	26,147
Current portion of long-term borrowings (note 12)	2,351	1,591
Accounts payable	92,825	35,603
Advances from customers	52,681	17,888
Deferred revenue	2,403	1,343
Income taxes payable (note 21)	1,233	31
FIN-48 payable (note 21)	83	83
Other payables and accrued expenses (note 10)	25,950	18,805
Current portion of operating lease liability (note 11)	2,480	1,417
Total current liabilities	195,207	102,908
Long-term borrowings (note 12)	23,080	17,979
Long-term operating lease liability (note 11)	2,119	2,880
Deferred tax liability (note 21)	1,293	1,286
Other long-term liabilities (note 13)	5,303	8,034
Total liabilities	227,002	133,087
Commitments and contingencies (note 21)
Stockholders' equity:
Additional paid in capital	110,776	102,004
Accumulated surplus	56,479	34,287
Accumulated other comprehensive income	5,759	4,857
Total ACM Research, Inc. stockholders' equity	173,016	141,150
Non-controlling interests	69,491	67,020
Total stockholders' equity	242,507	208,170
Total liabilities and stockholders' equity	469,509	341,257
Class A Common Stock [Member]
Stockholders' equity:
Common stock	2	2
Class B Common Stock [Member]
Stockholders' equity:
Common stock	$ 0	$ 0

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 0	$ 0
Class A Common Stock [Member]
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	150,000,000	50,000,000
Common stock, shares issued (in shares)	17,798,740	16,896,693
Common stock, shares outstanding (in shares)	17,798,740	16,896,693
Class B Common Stock [Member]
Stockholders' equity:
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	5,307,816	2,409,738
Common stock, shares issued (in shares)	1,707,605	1,802,606
Common stock, shares outstanding (in shares)	1,707,605	1,802,606

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Condensed Consolidated Statements of Operations and Comprehensive Income [Abstract]
Revenue (note 3)	$ 67,013	$ 47,665	$ 164,609	$ 111,062
Cost of revenue	37,328	27,324	95,199	61,137
Gross profit	29,685	20,341	69,410	49,925
Operating expenses:
Sales and marketing	6,363	3,924	17,460	11,524
Research and development	7,856	4,343	21,293	13,241
General and administrative	3,671	4,568	11,081	9,100
Total operating expenses, net	17,890	12,835	49,834	33,865
Income from operations	11,795	7,506	19,576	16,060
Interest income	33	179	113	834
Interest expense	(191)	(272)	(574)	(611)
Change in fair value of financial liability	0	(6,533)	0	(11,964)
Unrealized gain (loss) on trading securities	(919)	8,970	1,817	8,970
Other income (expenses), net	(255)	(1,759)	(683)	(933)
Equity income in net income of affiliates	421	182	1,036	539
Income before income taxes	10,884	8,273	21,285	12,895
Income tax benefit (expense) (note 21)	266	1,747	3,021	(416)
Net income	11,150	10,020	24,306	12,479
Less: Net income attributable to non-controlling interests and redeemable non-controlling interests	995	1,393	2,114	2,228
Net income available to common stockholders, basic and diluted	10,155	8,627	22,192	10,251
Comprehensive income:
Net income	11,150	10,020	24,306	12,479
Foreign currency translation adjustment	(409)	5,757	1,259	4,099
Comprehensive Income	10,741	15,777	25,565	16,578
Less: Comprehensive income attributable to non-controlling interests and redeemable non-controlling interests	757	2,698	2,471	3,614
Comprehensive income attributable to ACM Research, Inc.	$ 9,984	$ 13,079	$ 23,094	$ 12,964
Net income attributable to ACM Research, Inc. per common share (note 2):
Basic (in dollars per share)	$ 0.52	$ 0.47	$ 1.16	$ 0.57
Diluted (in dollars per share)	$ 0.46	$ 0.40	$ 1.02	$ 0.48
Weighted average common shares outstanding used in computing per share amounts (note 2):
Basic (in shares)	19,422,546	18,201,943	19,113,353	18,124,665
Diluted (in shares)	22,042,516	21,555,296	21,730,340	21,257,661

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]Common Stock Class A [Member]	Common Stock [Member]Common Stock Class B [Member]	Additional Paid-in Capital [Member]	Accumulated Surplus [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]	Total
Beginning balance at Dec. 31, 2019	$ 2	$ 0	$ 83,487	$ 15,507	$ (1,675)	$ 0	$ 97,321
Beginning balance (in shares) at Dec. 31, 2019	16,182,151	1,862,608
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	$ 0	0	10,251	0	1,585	11,836
Foreign currency translation adjustment	0	0	0	0	2,712	2,233	4,945
Exercise of stock options	$ 0	$ 0	2,191	0	0	0	2,191
Exercise of stock options (in shares)	592,946	0
Stock-based compensation	$ 0	$ 0	4,323	0	0	0	4,323
Conversion of class B common stock to Class A common stock	$ 0	$ 0	0	0	0	0	0
Conversion of class B common stock to Class A common stock (in shares)	60,002	(60,002)
Share cancellation	$ 0	$ 0	(9,715)	0	0	0	(9,715)
Share cancellation (in shares)	(242,681)	0
Issuance of warrants (note 15)	$ 0	$ 0	19,859	0	0	0	19,859
Exercise of stock warrants	$ 0	$ 0	0	0	0	0	0
Exercise of stock warrants (in shares)	64,717	0
Reclassification of redeemable non-controlling interest	$ 0	$ 0	0	0	0	59,958	59,958
Ending balance at Sep. 30, 2020	$ 2	$ 0	100,145	25,758	1,037	63,776	190,718
Ending balance (in shares) at Sep. 30, 2020	16,657,135	1,802,606
Beginning balance at Jun. 30, 2020	$ 2	$ 0	76,189	17,131	(3,415)	61,078	150,985
Beginning balance (in shares) at Jun. 30, 2020	16,250,092	1,802,606
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	$ 0	0	8,627	0	1,393	10,020
Foreign currency translation adjustment	0	0	0	0	4,452	1,305	5,757
Exercise of stock options	$ 0	$ 0	1,318	0	0	0	1,318
Exercise of stock options (in shares)	407,043	0
Stock-based compensation	$ 0	$ 0	2,779	0	0	0	2,779
Issuance of warrants (note 15)	0	0	19,859	0	0	0	19,859
Ending balance at Sep. 30, 2020	$ 2	$ 0	100,145	25,758	1,037	63,776	190,718
Ending balance (in shares) at Sep. 30, 2020	16,657,135	1,802,606
Beginning balance at Dec. 31, 2020	$ 2	$ 0	102,004	34,287	4,857	67,020	208,170
Beginning balance (in shares) at Dec. 31, 2020	16,896,693	1,802,606
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	$ 0	0	22,192	0	2,114	24,306
Foreign currency translation adjustment	0	0	0	0	902	357	1,259
Exercise of stock options	$ 0	$ 0	3,129	0	0	0	3,129
Exercise of stock options (in shares)	564,365	0
Stock-based compensation	$ 0	$ 0	3,823	0	0	0	3,823
Conversion of class B common stock to Class A common stock	$ 0	$ 0	0	0	0	0	0
Conversion of class B common stock to Class A common stock (in shares)	95,001	(95,001)
Exercise of stock warrants	$ 0	$ 0	1,820	0	0	0	1,820
Exercise of stock warrants (in shares)	242,681	0
Ending balance at Sep. 30, 2021	$ 2	$ 0	110,776	56,479	5,759	69,491	242,507
Ending balance (in shares) at Sep. 30, 2021	17,798,740	1,707,605
Beginning balance at Jun. 30, 2021	$ 2	$ 0	108,566	46,324	5,931	68,733	229,556
Beginning balance (in shares) at Jun. 30, 2021	17,668,409	1,707,605
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 0	$ 0	0	10,155	0	995	11,150
Foreign currency translation adjustment	0	0	0	0	(172)	(237)	(409)
Exercise of stock options	$ 0	$ 0	932	0	0	0	932
Exercise of stock options (in shares)	130,331	0
Stock-based compensation	$ 0	$ 0	1,278	0	0	0	1,278
Ending balance at Sep. 30, 2021	$ 2	$ 0	$ 110,776	$ 56,479	$ 5,759	$ 69,491	$ 242,507
Ending balance (in shares) at Sep. 30, 2021	17,798,740	1,707,605

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 11,150	$ 10,020	$ 24,306	$ 12,479
Adjustments to reconcile net income from operations to net cash used in operating activities
Depreciation and amortization			1,597	774
Loss on disposals of property, plant and equipment			0	1
Equity income in net income of affiliates	(421)	(182)	(1,036)	(539)
Unrealized gain on trading securities	919	(8,970)	(1,817)	(8,970)
Deferred income taxes			(4,666)	(4,632)
Stock-based compensation			3,823	4,323
Change in fair value of financial liability			0	11,964
Net changes in operating assets and liabilities:
Accounts receivable			(28,135)	(27,575)
Other receivables			(3,227)	(3,512)
Inventory			(87,613)	(18,362)
Prepaid expenses			(1,616)	(3,371)
Other long-term assets			(3,747)	(839)
Accounts payable			57,283	22,023
Advances from customers			34,879	(1,142)
Income tax payable			1,204	389
Other payables and accrued expenses			5,938	5,962
Deferred revenue			2,403	819
Other long-term liabilities			(3,398)	2,172
Net cash used in operating activities			(3,822)	(8,036)
Cash flows from investing activities:
Purchase of property and equipment			(5,059)	(3,583)
Purchase of intangible assets			(418)	(81)
Purchase of land-use-right			0	(9,331)
Prepayment for property			0	(6,978)
Purchase of trading securities			0	(14,680)
Net cash used in investing activities			(5,477)	(34,653)
Cash flows from financing activities:
Proceeds from short-term borrowings			17,988	31,068
Repayments of short-term borrowings			(28,988)	(16,881)
Proceeds from long-term borrowings			6,939	0
Repayments of long-term borrowings			(1,193)	0
Repayments of notes payable			0	(1,820)
Proceeds from stock option exercise to common stock			3,129	2,191
Proceeds from warrant exercise to common stock			1,820	0
Net cash provided by (used in) financing activities			(305)	14,558
Effect of exchange rate changes on cash, cash equivalents and restricted cash			2,874	2,475
Net (decrease) in cash, cash equivalents and restricted cash			(6,730)	(25,656)
Cash, cash equivalents and restricted cash at beginning of period			71,766	117,859	$ 117,859
Cash, cash equivalents and restricted cash at end of period	65,036	92,203	65,036	92,203	71,766
Supplemental disclosure of cash flow information:
Interest paid, net of capitalized interest			574	611
Cash paid for income taxes			606	4,606
Reconciliation of cash, cash equivalents and restricted cash in condensed consolidated statements of cash flows:
Cash and cash equivalents	65,036	92,203	65,036	92,203	$ 71,766
Restricted cash	$ 0	$ 0	0	0
Non-cash used in financing activities:
Warrant conversion to common stock			0	399
Share cancellation			0	9,715
Cashless exercise of stock options			118	0
Issuance of warrant for settlement of financial liability and cancellation of note receivable			$ 0	$ 19,859

DESCRIPTION OF BUSINESS

DESCRIPTION OF BUSINESS	9 Months Ended
	Sep. 30, 2021
DESCRIPTION OF BUSINESS [Abstract]
DESCRIPTION OF BUSINESS	NOTE 1 – DESCRIPTION OF BUSINESS A CM Research, Inc. (“ACM”) and its subsidiaries (collectively with ACM, the “Company”) develop, manufacture and sell wet cleaning and other equipment used to improve the manufacturing process and yield for advanced integrated chips. The Company markets and sells its wet-cleaning equipment under the brand name “Ultra C,” based on the Company’s proprietary Space Alternated Phase Shift (“SAPS”), Timely Energized Bubble Oscillation (“TEBO”), and Tahoe technologies. These tools are designed to remove random defects from a wafer surface efficiently, without damaging the wafer or its features, even at increasingly advanced process nodes. ACM was incorporated in California in 1998, and it initially focused on developing tools for manufacturing process steps involving the integration of ultra low-K materials and copper. The Company’s early efforts focused on stress-free copper-polishing technology, and it sold tools based on that technology in the early 2000s. In 2006 the Company established its operational center in Shanghai in the People’s Republic of China (the “PRC”), where it operates through ACM’s subsidiary ACM Research (Shanghai), Inc. (“ACM Shanghai”). ACM Shanghai was formed to help establish and build relationships with integrated circuit manufacturers in the PRC, and the Company initially financed its Shanghai operations in part through sales of non-controlling equity interests in ACM Shanghai. In 2007 the Company began to focus its development efforts on single-wafer wet-cleaning solutions for the front-end chip fabrication process. The Company introduced its SAPS megasonic technology, which can be applied in wet wafer cleaning at numerous steps during the chip fabrication process, in 2009. It introduced its TEBO technology, which can be applied at numerous steps during the fabrication of small node two-dimensional conventional and three-dimensional patterned wafers, in March 2016. The Company has designed its equipment models for SAPS and TEBO solutions using a modular configuration that enables it to create a wet-cleaning tool meeting the specific requirements of a customer, while using pre-existing designs for chamber, electrical, chemical delivery and other modules. In August 2018, the Company introduced its Ultra-C Tahoe wafer cleaning tool, which can deliver high cleaning performance with significantly less sulfuric acid than typically consumed by conventional high-temperature single-wafer cleaning tools. Based on its electro-chemical plating (“ECP”) technology, in 2019 the Company introduced its Ultra ECP ap, or “Advanced Packaging,” tool for bumping, or applying copper, tin and nickel to semiconductor wafers at the die-level, and its Ultra ECP map, or “Multi-Anode Partial Plating,” tool to deliver advanced electrochemical copper plating for copper interconnect applications in front-end wafer fabrication processes. The Company also offers a range of custom-made equipment, including cleaners, coaters and developers, to back-end wafer assembly and packaging factories, principally in the PRC. In 2011 ACM Shanghai formed a wholly owned subsidiary in the PRC, ACM Research (Wuxi), Inc. (“ACM Wuxi”), to manage sales and service operations. In November 2016 ACM redomesticated from California to Delaware pursuant to a merger in which ACM Research, Inc., a California corporation, was merged into a newly formed, wholly owned Delaware subsidiary, also named ACM Research, Inc. In June 2017 ACM formed a wholly owned subsidiary in Hong Kong, CleanChip Technologies Limited (“CleanChip”), to act on the Company’s behalf in Asian markets outside the PRC by, for example, serving as a trading partner between ACM Shanghai and its customers, procuring raw materials and components, performing sales and marketing activities, and making strategic investments. In August 2017 ACM purchased of ACM Shanghai’s equity interests held by Shanghai Science and Technology Venture Capital Co., Ltd. On November 8, 2017, ACM purchased the remaining of ACM Shanghai’s equity interest held by third parties, Shanghai Pudong High-Tech Investment Co., Ltd. (“PDHTI”) and Shanghai Zhangjiang Science & Technology Venture Capital Co., Ltd. (“ZSTVC”). At December 31, 2017, ACM owned all of the outstanding equity interests of ACM Shanghai, and indirectly through ACM Shanghai, owned all of the outstanding equity interests of ACM Wuxi. On September 13, 2017, ACM effectuated a 1-for-3 reverse stock split of Class A and Class B common stock. Unless otherwise indicated, all share numbers, per share amount, share prices, exercise prices and conversion rates set forth in these notes and the accompanying consolidated financial statements have been adjusted retrospectively to reflect the reverse stock split. On November 2, 2017, the Registration Statement on Form S-1 (File No. 333- 220451) for ACM’s initial public offering of Class A common stock was declared effective by the U.S. Securities and Exchange Commission. Shares of Class A common stock began trading on the Nasdaq Global Market on November 3, 2017, and the closing for the offering was held on November 7, 2017. In December 2017 ACM formed a wholly owned subsidiary in the Republic of Korea, ACM Research Korea CO., LTD. (“ACM Korea”), to serve customers based in Republic of Korea and perform sales, marketing, research and development activities for new products and solutions. In March 2019 ACM Shanghai formed a wholly owned subsidiary in the PRC, Shengwei Research (Shanghai), Inc. (“ACM Shengwei”), to manage activities related to addition of future long-term production capacity. In April 2019 CleanChip formed a wholly owned subsidiary in California, ACM Research (CA), Inc. (“ACM California”), to provide procurement services on behalf of ACM Shanghai In June 2019 ACM announced plans to complete, over the following three years, a listing (the “STAR Listing”) of shares of ACM Shanghai on the Shanghai Stock Exchange’s new Sci-Tech innovAtion boaRd, known as the STAR Market, and a concurrent initial public offering (the “STAR IPO”) of ACM Shanghai shares in the PRC. ACM Shanghai is currently ACM’s primary operating subsidiary, and at the time of announcement, was wholly owned by ACM. To meet a STAR Listing requirement that it have multiple independent stockholders in the PRC, ACM Shanghai completed private placements of its shares in June and November 2019, following which, as of September 30, 2020, the private placement investors held a total of 8.3% of the outstanding shares of ACM Shanghai and ACM Research held the remaining 91.7%. As part of the STAR Listing process, in June 2020 the ownership interests held by the private investors were reclassified from redeemable non-controlling interests to non-controlling interests as the redemption feature was terminated (note 19). I n preparation for the STAR IPO, ACM completed a reorganization in December 2019 that included the sale of all of the shares of CleanChip by ACM to ACM Shanghai impact on ACM’s c In August 2021 ACM formed a wholly owned subsidiary Singapore, ACM research (Singapore) PTE, Ltd. to perform sales, marketing, and other business development activities. The Company has direct or indirect interests in the following subsidiaries: Effective interest held as at Name of subsidiaries Place and date of incorporation September 30, 2021 December 31, 2020 ACM Research (Shanghai), Inc. PRC, May 2005 91.7 % 91.7 % ACM Research (Wuxi), Inc. PRC, July 2011 91.7 % 91.7 % CleanChip Technologies Limited Hong Kong, September 2017 91.7 % 91.7 % ACM Research Korea CO., LTD. Korea, December 2017 91.7 % 91.7 % Shengwei Research (Shanghai), Inc. PRC, March 2019 91.7 % 91.7 % ACM Research (CA), Inc. USA, April 2019 91.7 % 91.7 % ACM Research (Cayman), Inc. Cayman Islands, April 2019 100.0 % 100.0 % ACM Research (Singapore) PTE, Ltd. Singapore, August 2021 100.0 % 0.0 %

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 2 – SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation and Principles of Consolidation The Company’s condensed consolidated financial statements include the accounts of ACM and its subsidiaries, including ACM Shanghai and its subsidiaries, which include ACM Wuxi, ACM Shengwei and CleanChip (the subsidiaries of which include ACM California and ACM Korea). ACM’s subsidiaries are those entities in which ACM, directly or indirectly, controls a majority of the voting power. All significant intercompany transactions and balances have been eliminated upon consolidation. The accompanying condensed consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and the rules and regulations of the Securities and Exchange Commission for reporting on Form -Q. Accordingly, they do not include all the information and footnotes required by GAAP for complete financial statements. The accompanying condensed consolidated financial statements should be read in conjunction with the historical consolidated financial statements of the Company for the year ended December included in ACM’s Annual Report on Form -K for the year ended December . The accompanying condensed consolidated balance sheet as of September condensed consolidated statements of operations and comprehensive income for the and months ended September and condensed consolidated statements of changes in stockholders’ equity for the and months ended September and and condensed consolidated statements of cash flows for the months ended September and are unaudited. In the opinion of management, these unaudited condensed consolidated financial statements of the Company reflect all adjustments that are necessary for a fair presentation of the Company’s financial position and results of operations. Such adjustments are of a normal recurring nature, unless otherwise noted. The balance sheet as of September and the results of operations for the and months ended September are not necessarily indicative of the results to be expected for any future period. COVID-19 Assessment The outbreak of COVID- the coronavirus, has grown both in the United States and globally, and related government and private sector responsive actions have adversely affected the Company’s business operations. In December a series of emergency quarantine measures taken by the PRC government disrupted domestic business activities during the weeks after the initial outbreak of COVID- Since that time, an increasing number of countries, including the United States, have imposed restrictions on travel to and from the PRC and elsewhere, as well as general movement restrictions, business closures and other measures imposed to slow the spread of COVID- The situation continues to develop, and it is impossible to predict the effect and ultimate impact of the COVID- outbreak on the Company’s business operations and results. While the quarantine, social distancing and other regulatory measures instituted or recommended in response to COVID- are expected to be temporary, the duration of the business disruptions and related financial impact cannot be estimated at this time. The COVID- outbreak has been declared a worldwide health pandemic that could adversely affect the economies and financial markets of many countries, resulting in an economic downturn and changes in global economic policy that could reduce demand for the Company’s products and its customers’ chips and have a material adverse impact on the Company’s business, operating results and financial condition. Through September the Company had not experienced a significant negative impact of COVID- on its operations, capital and financial resources, including overall liquidity position. The Company continues to monitor the impact of the COVID-19 pandemic on all aspects of its business. The Company conducts substantially all of its product development, manufacturing, support and services in the PRC, and those activities have been directly impacted by the COVID- outbreak and related restrictions on transportation and public appearances. In February ACM Shanghai’s headquarters were closed for an additional beyond the normal Lunar New Year Holiday in accordance with Shanghai government restrictions related to the outbreak. The Company cannot assure that further closures or reductions of its PRC operations or production may not be necessary in upcoming months as the result of business interruptions arising from protective measures being taken by the PRC and other governmental agencies or of other consequences of the COVID- outbreak. The Company’s corporate headquarters are located in Alameda County in the San Francisco Bay Area of California. The effects of any future actions by the State of California, the San Francisco Department of Public Health, health officers of the San Francisco Bay Area counties or other local health officials that intended to mitigate the COVID-19 pandemic may negatively impact productivity, disrupt the business of the Company and delay timelines, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on the Company’s ability to conduct its business in the ordinary course. The prolonged and broad-based shift to a remote working environment continues to create inherent productivity, connectivity, and oversight challenges and could affect our ability to enhance, develop and support existing products and services, detect and prevent spam and problematic content, hold product sales and marketing events, and generate new sales leads, among others. In addition, the changed environment under which the Company is operating could have an effect on its internal controls over financial reporting as well as the Company’s ability to meet a number of its compliance requirements in a timely or quality manner. Additional and/or extended, governmental lockdowns, restrictions or new regulations could significantly impact the ability of our employees and vendors to work productively. Governmental restrictions have been globally inconsistent and it remains unclear when a return to worksite locations or travel will be permitted or what restrictions will be in place in those environments. As the Company continues to return its workforce in more office locations in it may experience increased costs as it prepares its facilities for a safe return to work environment and experiment with hybrid work models, in addition to potential effects on its ability to compete effectively and maintain its corporate culture. Extended periods of interruption to the Company’s corporate, development or manufacturing facilities due to the COVID- outbreak could cause the Company to lose revenue and market share, which would depress its financial performance and could be difficult to recapture. The Company’s business may also be harmed if travel to or from the PRC or the United States continues to be restricted or inadvisable or if members of management and other employees are absent because they contract the coronavirus, they elect not to come to work due to the illness affecting others in the Company’s office or laboratory facilities, or they are subject to quarantines or other governmentally imposed restrictions. Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the balance sheet date and the reported revenues and expenses during the reported period in the consolidated financial statements and accompanying notes. The Company’s significant accounting estimates and assumptions include, but are not limited to, those used for the valuation and recognition of fair value of trading securities, stock-based compensation arrangements and warrant liability, realization of deferred tax assets, assessment for impairment of long-lived assets, allowance for doubtful accounts, inventory valuation for excess and obsolete inventories, lower of cost and market value or net realizable value of inventories, depreciable lives of property and equipment and useful life of intangible assets. Management evaluates these estimates and assumptions on a regular basis. Actual results could differ from those estimates and assumptions. Basic and Diluted Net Income per Common Share Basic and diluted net income per common share are calculated as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net income $ 11,150 $ 10,020 $ 24,306 $ 12,479 Less: Net income attributable to non-controlling interests and redeemable non-controlling interests 995 1,393 2,114 2,228 Net income available to common stockholders, basic and diluted $ 10,155 $ 8,627 $ 22,192 $ 10,251 Weighted average shares outstanding, basic 19,422,546 18,201,943 19,113,353 18,124,665 Effect of dilutive securities 2,619,970 3,353,353 2,616,987 3,132,996 Weighted average shares outstanding, diluted 22,042,516 21,555,296 21,730,340 21,257,661 Net income per common share: Basic $ 0.52 $ 0.47 $ 1.16 $ 0.57 Diluted $ 0.46 $ 0.40 $ 1.02 $ 0.48 ACM has been authorized to issue Class A and Class B common stock since redomesticating in Delaware in November The classes of common stock are substantially identical in all material respects, except for voting rights. Since ACM did not declare any dividends during the and nine months ended September and the net income per common share attributable to each class is the same under the “ -class” method. As such, the classes of common stock have been presented on a combined basis in the condensed consolidated statements of operations and comprehensive income and in the above computation of net income per common share. Diluted net income per common share reflects the potential dilution from securities, including stock options and issued warrants, that could share in ACM’s earnings. Certain potential dilutive securities were excluded from the net income per share calculation because the impact would be anti-dilutive. ACM’s potential dilutive securities consist of warrants and stock options for the months ended September ’ Concentration of Credit Risk Financial instruments that potentially subject the Company to credit risk consist principally of cash and cash equivalents and accounts receivable. The Company deposits and invests its cash with financial institutions that management believes are creditworthy. The Company is potentially subject to concentrations of credit risks in its accounts receivable. For the nine months ended September Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2019 - 12, Income Taxes (Topic 740) : Simplifying the Accounting for Income Taxes . ASU 2019 - 12 simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. It also improves consistent application of and simplifies GAAP for other areas of Topic 740 by clarifying and amending existing guidance. The Company adopted ASU 2019 - 12 on January 1, 2021. The adoption of ASU 2019 - 12 did not have a material impact on the Company’s condensed consolidated financial statements. In March the FASB issued ASU No. - Reference Rate Reform (Topic : Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU - provide optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The Company adopted ASU - on January The adoption of ASU - did not have a material impact on the Company’s condensed consolidated financial statements. Recent Accounting Pronouncements Not Yet Adopted In June the FASB issued ASU - Financial Instruments-Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments . ASU - replaced the pre-existing incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU - requires use of a forward-looking expected credit loss model for accounts receivables, loans and other financial instruments. ASU - is effective for fiscal years beginning after December with early adoption permitted. In October the FASB issued ASU - Financial Instruments – Credit Losses (Topic 326) , Derivatives and Hedging (Topic 815) and Leases (Topic 842) , which defers the effective date for public filers that are considered small reporting companies (“SRC”) as defined by the U.S. Securities and Exchange Commission (“SEC”) to fiscal years beginning after December including interim periods within those fiscal years. Since the Company was eligible to be an SRC based on its SRC determination as of November (which is the issuance date of ASU - in accordance with SEC regulations, the Company will adopt the standards for the year beginning January Adoption of the standard requires using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the effective date to align existing credit loss methodology with the new standard. The Company is evaluating the impact of this standard on its consolidated financial statements, including accounting policies, processes and systems and expects the standard will have a minor impact on its consolidated financial statements.

REVENUE FROM CONTRACTS WITH CUS

REVENUE FROM CONTRACTS WITH CUSTOMERS	9 Months Ended
	Sep. 30, 2021
REVENUE FROM CONTRACTS WITH CUSTOMERS [Abstract]
REVENUE FROM CONTRACTS WITH CUSTOMERS	NOTE 3 – REVENUE FROM CONTRACTS WITH CUSTOMERS The Company assesses revenues based upon the nature or type of goods or services it provides and the geographic location of the related businesses. The following tables present disaggregated revenue information: Three Months Ended , Nine September 30 2021 2020 2021 2020 Single wafer cleaning, Tahoe and semi-critical cleaning equipment $ 49,448 $ 38,344 $ 127,322 $ 94,468 ECP (front-end and packaging), furnace and other technologies 8,200 4,850 13,750 9,340 Advanced packaging (excluding ECP), services & spares 9,365 4,471 23,537 7,254 Total Revenue By Product Category $ 67,013 $ 47,665 $ 164,609 $ 111,062 Wet cleaning and other front-end processing tools $ 49,448 $ 38,344 $ 127,322 $ 98,958 Advanced packaging, other processing tools, services and spares 17,565 9,321 37,287 12,104 Total Revenue Fron t-end $ 67,013 $ 47,665 $ 164,609 $ 111,062 Three Months Ended , Nine September 30 2021 2020 2021 2020 Mainland China $ 66,887 $ 46,881 $ 164,319 $ 110,174 Other Regions 126 784 290 888 $ 67,013 $ 47,665 $ 164,609 $ 111,062

ACCOUNTS RECEIVABLE

ACCOUNTS RECEIVABLE	9 Months Ended
	Sep. 30, 2021
ACCOUNTS RECEIVABLE [Abstract]
ACCOUNTS RECEIVABLE	NOTE 4 – ACCOUNTS RECEIVABLE A t September 30, 2021 and December 31, 2020 accounts receivable consisted of the followin September 30, 2021 December 31, 2020 Accounts receivable $ 84,787 $ 56,441 Less: Allowance for doubtful accounts - - Total $ 84,787 $ 56,441 T he Company reviews accounts receivable on a periodic basis and makes general and specific allowances when there is doubt as to the collectability of individual balances. allowance for doubtful accounts was considered necessary at September 30, 2021 and December 31, 2020

INVENTORIES

INVENTORIES	9 Months Ended
	Sep. 30, 2021
INVENTORIES [Abstract]
INVENTORIES	NOTE 5 – INVENTORIES At September 30, 2021 and December 31, 2020 inventory consisted of the following: September 30, 2021 December 31, 2020 Raw materials $ 65,029 $ 32,391 Work in process 29,682 23,871 Finished goods 81,898 32,377 Total inventory $ 176,609 $ 88,639 At September 30, 2021 and December 31, 2020, the Company held an inventory reserve of $1,112 and $1,140, respectively. At September 30, 2021 and December 31, 2020, finished goods inventory included system shipments of first-tools to existing or prospective customers, for which ownership does not transfer until customer acceptance or customer purchase, totaling $81,898 and $32,275, respectively. Those tools are carried at cost until ownership is transferred. At September 30, 2021 and December 31, 2020, finished goods inventory included tools for which customers are contractually obligated to take ownership upon acceptance totaling $58,928 and $20,834, respectively.

PROPERTY, PLANT AND EQUIPMENT,

PROPERTY, PLANT AND EQUIPMENT, NET	9 Months Ended
	Sep. 30, 2021
PROPERTY, PLANT AND EQUIPMENT, NET [Abstract]
PROPERTY, PLANT AND EQUIPMENT, NET	NOTE 6 – PROPERTY, PLANT AND EQUIPMENT, NET At September 30, 2021 and December 31, 2020, property, plant and equipment consisted of the following: September 30, 2021 December 31, 2020 Manufacturing equipment $ 6,992 $ 5,966 Office equipment 1,642 1,047 Transportation equipment 214 216 Leasehold improvement 2,932 2,398 Total cost 11,780 9,627 Less: Total accumulated depreciation (5,120 ) (3,745 ) Construction in progress 3,345 2,310 Total property, plant and equipment, net $ 10,005 $ 8,192 Depreciation expense was $ and $ for the three months ended September 30, 2021 and 2020, respectively, and and for the months ended September 30, 2021 and 2020, respectively.

LAND USE RIGHT, NET

LAND USE RIGHT, NET	9 Months Ended
	Sep. 30, 2021
LAND USE RIGHT, NET [Abstract]
LAND USE RIGHT, NET	NOTE 7 – LAND USE RIGHT, NET A summary of land use right is as follows: September 30, 2021 December 31, 2020 Land use right purchase amount $ 9,801 $ 9,744 Less: Accumulated amortization (245 ) (98 ) Land use right, net $ 9,556 $ 9,646 In 2020 ACM Shanghai, through its wholly owned subsidiary ACM Shengwei, entered into an agreement for a 50-year land use right in the Lingang region of Shanghai. In July 2020 ACM Shengwei began a multi-year construction project for a new 1,000,000 square foot development and production center that will incorporate new manufacturing systems and automation technologies, and will provide floor space to support significantly increase production capacity and related research and development activities. Amortization expense was $49 for the three months ended September 30, 2021, and $147 for the nine months ended September 30, 2021. The remaining amortization of land use right for each of the five succeeding years is as follows: Year ending December 31, 2021 $ 49 2022 196 2023 196 2024 196 2025 196

OTHER LONG-TERM ASSETS

OTHER LONG-TERM ASSETS	9 Months Ended
	Sep. 30, 2021
OTHER LONG-TERM ASSETS [Abstract]
OTHER LONG-TERM ASSETS	NOTE 8 – OTHER LONG-TERM ASSETS At September 30, 2021 and December 31, 2020, other long-term assets consisted of the following: September 30, 2021 December 31, 2020 Prepayment for property - Lingang $ 40,433 $ 39,450 Prepayment for property, plant and equipment and other non-current assets 1,692 - Prepayment for property - lease deposit 422 - Security deposit for land use right 760 756 Others 936 290 Total other long-term assets $ 44,243 $ 40,496 The prepayment for property - Lingang is for the housing in Lingang, Shanghai, which consists of (1) the contractual amount to acquire the property and (2) capitalized interest charges on the long-term loan related to acquisition of the property, which amounted to $ as of September 30, 2021. The property is pledged for a long-term loan from China Merchants Bank (note 12).

SHORT-TERM BORROWINGS

SHORT-TERM BORROWINGS	9 Months Ended
	Sep. 30, 2021
SHORT-TERM BORROWINGS [Abstract]
SHORT-TERM BORROWINGS	NOTE 9 – SHORT-TERM BORROWINGS At September 30, 2021 and December 31, 2020, short-term borrowings consisted of the following: September 30, 2021 December 31, 2020 Line of credit up to RMB 80,000 1)due on April 1, 2021 with an annual interest rate of 4.70 March 23, 2021 $ - $ 4,599 2)due on June 27, 2021 with an annual interest rate of 4.25 June 28, 2021 - 1,380 3)due on April 29, 2021 with an annual interest rate of 2.80 March 23, 2021 - 820 4)due on June 27, 2021 with an annual interest rate of 2.70 June 25, 2021 - 2,080 Line of credit up to RMB 20,000 1)due on April 12, 2021 with an annual interest rate of 4.65% and fully repaid on April 12, 2021. - 1,533 2)due on May 24, 2021 with an annual interest rate of 3.65% and fully repaid on May 24, 2021. - 1,533 Line of credit up to RMB 70,000 from Bank of Shanghai Pudong Branch, 1)due on May 27, 2021 with an annual interest rate of 4.68%. *2 and fully repaid on May 27, 2021. - 2,575 2)due on June 27, 2021 with an annual interest rate of 4.68%. *2 and fully repaid on March 29, 2021. - 1,380 3)due on May 28, 2021 with an annual interest rate of 3.48%. *2 and fully repaid on May 28, 2021. - 2,442 4)due on June 7, 2021 with an annual interest rate of 3.50%. *2 and fully repaid on June 7, 2021. - 1,521 5)due on June 16, 2021 with an annual interest rate of 3.50%. *2 and fully repaid on June 16, 2021. - 1,838 Line of credit up to RMB 80,000 from China Merchants Bank, 1)due on August 10, 2021 with annual interest rate of 3.85% and fully repaid on August 10, 2021. - 1,380 2)due on August 25, 2021 with annual interest rate of 3.85% and fully repaid on August 25, 2021. - 3,066 3)due on February 1, 2022 with annual interest rate of 3.85%. 1,388 - 4)due on May 26, 2022 with annual interest rate of 3.9%. 1,388 - 5)due on February 2, 2022 with annual interest rate of 3.95%. 1,465 - 6)due on February 2, 2022 with annual interest rate of 3.95%. 1,465 - 7)due on February 2, 2022 with annual interest rate of 3.95%. 1,387 - Line of credit up to RMB 100,000 from Bank of Shanghai Pudong Branch, 1)due on June 7, 2022 with an annual interest rate of 2.7%. *3 4,618 - Line of credit up to RMB 40,000 from Bank of China, 1)due on June 15, 2022 with an annual interest rate of 3.86%. 3,068 - Line of credit up to KRW 500,000 from Industrial Bank of Korea (IBK) 1)due on July 11, 2022 with an annual interest rate of 5.40%. *4 422 - Total $ 15,201 $ 26,147 *1 Guaranteed by ACM’s Chief Executive Officer *2 Guaranteed by ACM’s Chief Executive Officer and CleanChip *3 Guaranteed by CleanChip *4 Guaranteed by ACM Korea’s Chief Executive Officer For the three months ended September 30, 2021 and 2020, interest expense related to short-term borrowings amounted to $176 and $272, respectively, and $556 and $611 for the nine months ended September 30, 2021 and 2020.

OTHER PAYABLE AND ACCRUED EXPEN

OTHER PAYABLE AND ACCRUED EXPENSES	9 Months Ended
	Sep. 30, 2021
OTHER PAYABLE AND ACCRUED EXPENSES [Abstract]
OTHER PAYABLE AND ACCRUED EXPENSES	NOTE 10 – OTHER PAYABLE AND ACCRUED EXPENSES At September 30, 2021 and December 31, 2020, other payable and accrued expenses consisted of the following: September 30, 2021 December 31, 2020 Accrued commissions 10,527 7,127 Accrued warranty 5,117 3,975 Accrued payroll 3,492 3,068 Accrued professional fees 40 384 Accrued machine testing fees 1,825 1,595 Others 4,949 2,656 Total $ 25,950 $ 18,805

LEASES

LEASES	9 Months Ended
	Sep. 30, 2021
LEASES [Abstract]
LEASES	NOTE 11 – LEASES The Company leases space under non-cancelable operating leases for several office and manufacturing locations. These leases do not have significant rent escalation holidays, concessions, leasehold improvement incentives, or other build-out clauses. Further, the leases do not contain contingent rent provisions. Most leases include one or more options to renew. The exercise of lease renewal options is typically at the Company’s sole discretion; therefore, the majority of renewals to extend the lease terms are not included in the Company’s right-of-use assets and lease liabilities as they are not reasonably certain of exercise. The Company regularly evaluates the renewal options, and when they are reasonably certain of exercise, the Company includes the renewal period in its lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of the lease payments. The Company has a centrally managed treasury function; therefore, based on the applicable lease terms and the current economic environment, it applies a portfolio approach for determining the incremental borrowing rate. The components of lease expense were as follows: Three Months Ended September 30, Nine September 30 2021 2020 2021 2020 Operating lease cost $ 632 $ 384 $ 1,807 $ 1,139 Short-term lease cost 105 73 258 170 Lease cost $ 737 $ 457 $ 2,065 $ 1,309 Supplemental cash flow information related to operating leases was as follows for the three and nine months ended September 30, 2021 and 2020 Three Months Ended September 30, Nine September 30 2021 2020 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflow from operating leases $ 737 $ 457 $ 2,065 $ 1,309 Maturities of lease liabilities for all operating leases were as follows as of September 30, 2021 December 31, 2021 631 2022 2,292 2023 1,020 2024 914 2025 19 Total lease payments 4,876 Less: Interest (277 ) Present value of lease liabilities $ 4,599 The weighted average remaining lease terms and discount rates for all operating leases were as follows as of September 30 and December : September 30, 2021 December 31, 2020 Remaining lease term and discount rate: Weighted average remaining lease term (years) 1.50 2.11 Weighted average discount rate 4.58 % 5.14 %

LONG-TERM BORROWINGS

LONG-TERM BORROWINGS	9 Months Ended
	Sep. 30, 2021
LONG-TERM BORROWINGS [Abstract]
LONG-TERM BORROWINGS	NOTE 12 – LONG-TERM BORROWINGS At September 30 and December long-term borrowings consisted of the following: September 30, 2021 December 31, 2020 Loan from China Merchants Bank $ 18,492 $ 19,570 Loans from Bank of China $ 6,939 - Less: Current portion (2,351 ) (1,591 ) $ 23,080 $ 17,979 The loan from China Merchants Bank is for the purpose of purchasing property in Lingang, Shanghai. The loan is repayable in installments with the last installment due in November 2030 with an annual interest rate of . The loan is pledged by the property of ACM Shengwei and guaranteed by ACM Shanghai. As of September 30 the right certificate of the pledged property has not been obtained and the procedures of the formal pledge registration in the bank had not been completed. The loans from Bank of China are for the purpose of funding ACM Shanghai research activities. The loans bear interest at an annual rate of and is repayable in installments, with the last installments due in June 2024 and September 2024 Scheduled principal payments for the outstanding long-term loan as of September 30 are as follows: Year ending December 31 2021 $ 484 2022 2,370 2023 2,450 2024 7,313 2025 and onwards 12,814 $ 25,431 For the months ended September 30 interest related to long-term borrowings of was incurred, of which was charged to interest expenses and $ was capitalized as other long-term assets. For the nine months ended September 30, 2021, interest related to long-term borrowings of $ was incurred, of which $ was charged to interest expenses and $ was capitalized as other long-term assets .

OTHER LONG-TERM LIABILITIES

OTHER LONG-TERM LIABILITIES	9 Months Ended
	Sep. 30, 2021
OTHER LONG-TERM LIABILITIES [Abstract]
OTHER LONG-TERM LIABILITIES	NOTE 13 – OTHER LONG-TERM LIABILITIES Other long-term liabilities represent government subsidies received from PRC governmental authorities for development and commercialization of certain technology but not yet recognized. As of September 30 and December other long-term liabilities consisted of the following unearned government subsidies: September 30, 2021 December 31, 2020 Subsidies to Stress Free Polishing project, commenced in 2008 and 2017 $ 949 $ 1,266 Subsidies to Electro Copper Plating project, commenced in 2014 901 2,156 Subsidies to Polytetrafluoroethylene, commenced in 2018 - 130 Subsidies to Tahoe-Single Bench Clean, commenced in 2020 185 1,544 Subsidies to Backside Clean-YMTC National Project, commenced in 2020 2,779 2,591 Other 489 347 Total $ 5,303 $ 8,034

LONG-TERM INVESTMENT

LONG-TERM INVESTMENT	9 Months Ended
	Sep. 30, 2021
LONG-TERM INVESTMENT [Abstract]
LONG-TERM INVESTMENT	NOTE 14 – LONG-TERM INVESTMENT On September ACM and Ninebell Co., Ltd. (“Ninebell”), a Korean company that is of the Company’s principal material suppliers, entered into an ordinary share purchase agreement, effective as of September pursuant to which Ninebell issued to ACM ordinary shares representing of Ninebell’s post-closing equity for a purchase price of and a common stock purchase agreement, effective as of September pursuant to which ACM issued shares of Class A common stock to Ninebell for a purchase price of at per share. The investment in Ninebell is accounted for under the equity method. On June ACM Shanghai and Shengyi Semiconductor Technology Co., Ltd. (“Shengyi”), a company based in Wuxi, China that is of the Company’s component suppliers, entered into an agreement pursuant to which Shengyi issued to ACM Shanghai shares representing of Shengyi’s post-closing equity for a purchase price of The investment in Shengyi is accounted for under the equity method. On September ACM Shanghai, entered into a Partnership Agreement with other investors, as limited partners, and Beijing Shixi Qingliu Investment Co., Ltd., as general partner and manager, with respect to the formation of Hefei Shixi Chanheng Integrated Circuit Industry Venture Capital Fund Partnership (LP), a Chinese limited partnership based in Hefei, China. Pursuant to such Partnership Agreement, on September ACM Shanghai invested RMB ( , which represented of the partnership’s total subscribed capital. The investment in Hefei Shixi Chanheng Integrated Circuit Industry Venture Capital Fund Partnership (LP) is accounted for under the equity method in accordance with ASC - -S - The Company treats the equity investment in the consolidated financial statements under the equity method. Under the equity method, the investment is initially recorded at cost, adjusted for any excess of the Company’s share of the incorporated-date fair values of the investee’s identifiable net assets over the cost of the investment (if any). Thereafter, the investment is adjusted for the post incorporation change in the Company’s share of the investee’s net assets and any impairment loss relating to the investment. September 30, 2021 December 31, 2020 Ninebell $ 2,713 $ 1,666 Shengyi 186 134 Hefei Shixi 4,509 4,540 Total $ 7,408 $ 6,340 The Company’s share of equity investees’ net income was and for the three months ended September 30, 2021 and 2020, respectively, and $ and $ for the nine months ended September 30, 2021 and 2020, respectively, which amounts were included in equity income in net income of affiliates in the accompanying condensed consolidated statements of operations and comprehensive income.

FINANCIAL LIABILITY CARRIED AT

FINANCIAL LIABILITY CARRIED AT FAIR VALUE	9 Months Ended
	Sep. 30, 2021
FINANCIAL LIABILITY CARRIED AT FAIR VALUE [Abstract]
FINANCIAL LIABILITY CARRIED AT FAIR VALUE	NOTE 15 – FINANCIAL LIABILITY CARRIED AT FAIR VALUE In December 2016 Shengxin (Shanghai) Management Consulting Limited Partnership (“SMC”) paid 20,123,500 RMB ($2,981 as of the date of funding) (the “SMC Investment”) to ACM Shanghai as an investment pursuant to terms to be subsequently negotiated. SMC is a PRC limited partnership partially owned by employees of ACM Shanghai. In March 2017 (a) ACM issued to SMC a warrant (the “2017 Warrant”) exercisable to purchase 397,502 shares of Class A common stock at a price of $7.50 per share, for a total exercise price of $2,981, and (b) ACM Shanghai agreed to repay the SMC Investment within 60 days after the exercise of the 2017 Warrant. In March 2018 SMC exercised the 2017 Warrant in full, as a result of which (1) ACM issued 397,502 shares of Class A common stock to SMC (the “2017 Warrant Shares”), (2) SMC borrowed the funds to pay the 2017 Warrant exercise price pursuant to a senior secured promissory note (the “SMC Note”) in the principal amount of $2,981 issued to ACM Shanghai, which in turn issued to ACM a promissory note (the “Intercompany Note”) in the principal amount of $2,981 in payment of the 2017 Warrant exercise price. Each of the SMC Note and the Intercompany Note bore interest at a rate of 3.01% per annum and matured on August 17, 2023. The SMC Note was secured by a pledge of the 2017 Warrant Shares. In connection with its follow-on public offering of Class A common stock in August 2019, ACM agreed to purchase a total of 154,821 of the 2017 Warrant Shares from SMC at a per share price of $13.195, of which (a) $1,161 was applied to reduce SMC’s obligations to ACM Shanghai under the SMC Note, and which ACM then withheld for its own account and applied to reduce ACM Shanghai’s obligations to ACM under the Intercompany Note, and (b) the remaining $882 was paid to SMC. In a separate transaction, ACM Shanghai repaid $1,161 of the SMC Investment in cash, which reduced the amount of the SMC Investment due to SMC to $1,820. The SMC Note and SMC Investment were offsetting items in the Company’s consolidated balance sheet in accordance with ASC 210-20-45-1 up to April 30, 2020. In preparation for the STAR IPO, ACM Shanghai was required to terminate its financial relationship with SMC. In order to facilitate such termination, on April 30, 2020, ACM entered into two agreements relating to outstanding obligations among ACM Research, ACM Shanghai and SMC. Pursuant to such agreements: (i) ACM Shanghai assigned to ACM its rights under the SMC Note, including the right to receive payment of the $1,820 payable thereunder; (ii) ACM cancelled the outstanding $1,820 obligation of ACM Shanghai under the Intercompany Note; (iii) SMC surrendered its remaining 242,681 2017 Warrant Shares to ACM Research; and (iv) in exchange for such 242,681 2017 Warrant Shares, ACM agreed to deliver to SMC certain consideration (“SMC Consideration”) agreed upon by ACM Research and SMC, subject to obtaining certain PRC regulatory approvals. Under the agreements, if the required approvals were not obtained by December 31, 2023, ACM would cancel the SMC Note as consideration for the 242,681 2017 Warrant Shares. In a separate transaction in April 2020, ACM Shanghai repaid the remaining $1,820 of the SMC Investment in cash. Beginning April 30, 2020, the SMC Consideration was accounted for as a financial liability, and the Company applied the fair value measurement option to value the SMC Consideration in accordance with ASC 825-10-15-4a. On April 30, 2020, the SMC Consideration was $9,715, which reflected cancellation of the 2017 Warrant Shares and was recorded in equity. The financial liability was remeasured to fair value as of the end of each subsequent reporting period. On July 29, 2020, ACM and SMC entered into an amended agreement under which, in settlement of the SMC Consideration, ACM issued to SMC a warrant (the “2020 Warrant”) to purchase 242,681 shares of Class A common stock at a purchase price of $7.50 per share, and ACM cancelled the SMC Note. The financial liability was remeasured to fair value of $21,679 as of July 29, 2020, and was retired with the issuance of the 2020 Warrant. The Company recognized a change in fair value of financial liability of $11,964 for the year ended December 31, 2020, which was reflected in the consolidated statement of operations. The Company recorded the difference of $19,859 between the 2020 Warrant of $21,679 and the SMC Note of $1,820 into equity. The 2020 Warrant was initially measured at fair value at the issuance date and classified as equity permanently in accordance with ASC 815. The fair value of the 2020 Warrant amounted to $21,679, based on the grant date using the Black-Scholes valuation model with the following assumptions: July 29, 2020 Fair value of common share(1) $ 89.28 Expected term in years(2) 3.42 Volatility(3) 47.42 % Risk-free interest rate(4) 0.15 % Expected dividend(5) 0 % (1) Fair value of Class A common stock was the closing market price of the Class A common stock on July 29, 2020. (2) Expected term of share options was based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110. (3) Volatility was calculated based on the historical volatility of the stock of companies comparable to ACM in the period equal to the expected term of each grant. (4) Risk-free interest rate was based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant. (5) Expected dividend was assumed to be 0%, as ACM had no history or expectation of paying a dividend on its common stock. On June 9, 2021, subsequent to its obtaining the necessary PRC approvals, SMC exercised the 2020 Warrant by paying the $ exercise price to ACM and surrendering the 2020 Warrant to ACM. In return, ACM delivered shares of ACM Class A common stock to SMC.

TRADING SECURITIES

TRADING SECURITIES	9 Months Ended
	Sep. 30, 2021
TRADING SECURITIES [Abstract]
TRADING SECURITIES	NOTE 16 – TRADING SECURITIES Pursuant to a Partnership Agreement dated (the “Partnership Agreement”) and a Supplementary Agreement thereto dated (the “Supplementary Agreement”), ACM Shanghai became a limited partner of Qingdao Fortune-Tech Xinxing Capital Partnership (L.P.), a Chinese limited partnership based in Shanghai, China (the “Partnership”) of which China Fortune-Tech Capital Co., Ltd serves as general partner and unaffiliated entities serve, with ACM Shanghai, as limited partners. The Partnership was formed to establish a special fund that would purchase, in a strategic placement, shares of Semiconductor Manufacturing International Corporation, (“SMIC”) to be listed on the STAR Market. SMIC is a Shanghai-based foundry that has been a customer of the Company’s single-wafer wet-cleaning tools. The limited partners of the Partnership contributed to the fund a total of RMB billion ($ ), of which ACM Shanghai contributed RMB million ($ million), or of the total contribution, on . Upon the closing of the SMIC offering in , the initial number of SMIC shares owned by the Partnership was apportioned to all of the limited partners in proportion to their respective capital contributions ( in the case of ACM Shanghai). All of the SMIC shares acquired by the Partnership are subject, under applicable Chinese laws, to lock-up restrictions that prevent sales of the shares for year after the shares were acquired. Thereafter an individual limited partner will be able to instruct the general partner to sell, on behalf of the limited partner, all or a portion of the limited partner’s apportioned shares, subject to compliance with all laws, regulations, trading rules, the Partnership Agreement and the Supplementary Agreement. Alternatively, following the lock-up period, limited partners holding at least of the total SMIC shares held by the Partnership will be able, pursuant to a call auction in accordance with the Supplementary Agreement, to cause the general partner to arrange to sell all of the shares desired to be offered by each of the limited partners that complies with procedural requirements provided in the Supplementary Agreement. As SMIC was listed on the STAR Market in July 2020, ACM Shanghai’s investment is accounted for as trading securities and is stated at fair market value. At December 31, 2020, the fair market value is classified as Level of the hierarchy established under ASC with valuations based on quoted prices for identical securities in active markets, less a discount applied to reflect the remaining lock-up period. Following the expiration of the lock-up period in July 2021, the trading securities are stated at fair market value, which is classified as Level 1 of the hierarchy established under ASC 820 with valuations based on quoted prices for identical securities in active markets at September 30, 2021. The components of trading securities were as follows: September 30, 2021 December 31, 2020 Trading securities listed in Shanghai Stock Exchange Cost $ 15,108 $ 15,020 Market value $ 30,219 $ 28,239 Unrealized gain (loss) on trading securities, net of

RELATED PARTY BALANCES AND TRAN

RELATED PARTY BALANCES AND TRANSACTIONS	9 Months Ended
	Sep. 30, 2021
RELATED PARTY BALANCES AND TRANSACTIONS [Abstract]
RELATED PARTY BALANCES AND TRANSACTIONS	NOTE 17 – RELATED PARTY BALANCES AND TRANSACTIONS Prepaid expenses September 30, 2021 December 31, 2020 Ninebell $ 2,192 $ 1,607 Accounts payable September 30, 2021 December 31, 2020 Ninebell $ 6,340 $ 2,898 Shengyi 1,920 1,195 Total $ 8,260 $ 4,093 Three Months Ended , Nine Months Ended , Purchase of materials 2021 2020 2021 2020 Ninebell $ 7,455 $ 4,029 $ 21,833 $ 9,552 Shengyi 1,108 599 1,753 1,113 Total $ 8,563 $ 4,628 $ 23,586 $ 10,665 Three Months Ended September 30, Nine Months Ended September 30, Service fee charged by 2021 2020 2021 2020 Shengyi $ 144 $ 14 $ 403 $ 204 Ninebell - 22 - 22 Total $ 144 $ 36 $ 403 $ 226

COMMON STOCK

COMMON STOCK	9 Months Ended
	Sep. 30, 2021
COMMON STOCK [Abstract]
COMMON STOCK	NOTE 18 – COMMON STOCK At December 31, 2020, ACM was authorized to issue 50,000,000 shares of Class A common stock and 2,409,738 shares of Class B common stock, each with a par value of $0.0001. On July 13, 2021, the Company filed a certificate of amendment to its restated certificate of incorporation with the Secretary of State of the State of Delaware. The amendment i) increased the authorized number of shares of Class A common stock from 50,000,000 to 150,000,000 with 60,000,000 of the 100,000,000 additional authorized shares of Class A common stock reserved for issuance only as dividends on outstanding shares of Class A common stock; ii) increased the authorized number of shares of Class B common stock from 2,409,738 to 5,307,816, with all of the authorized but unissued shares of Class B common stock being available for issuance only as dividends on outstanding shares of Class B common stock; and iii) removed a now obsolete provision related to the automatic conversion of Class B common stock into Class A common stock. The amendment to ACM’s certificate of incorporation that increased the number of authorized Class A common stock and Class B common stock was approved by ACM’s stockholders on June 2, 2021. As a result, at September 30, 2021, ACM is authorized to issue 150,000,000 shares of Class A common stock and 5,307,816 shares of Class B common stock, each with a par value of $0.0001. Each share of Class A common stock is entitled to one vote, and each share of Class B common stock is entitled to twenty votes and is convertible at any time into one share of Class A common stock. Shares of Class A common stock and Class B common stock are treated equally, identically and ratably with respect to any dividends declared by the Board of Directors unless the Board of Directors declares different dividends to the Class A common stock and Class B common stock by getting approval from a majority of common stockholders. During the three months ended September 30, 2021, ACM issued 130,331 shares of Class A common stock upon option exercises by employees and non-employees. During the nine months ended September 30, 2021, ACM issued 564,365 shares of Class A common stock upon option exercises by employees and non-employees, and an additional 95,001 shares of Class A common stock upon conversion of an equal number of shares of Class B common stock. During the nine months ended September 30, 2021, ACM issued 242,681 shares of Class A common stock upon the warrant exercise by SMC (Note 15). During the three months ended September 30, 2020, ACM issued 407,043 shares of Class A common stock upon option exercises by employees and non-employees. During the nine months ended September 30, 2020, ACM issued shares of Class A common stock upon option exercises by employees and non-employees, and an additional shares of Class A common stock upon conversion of an equal number of shares of Class B common stock. During the nine months ended September 30, 2020, ACM issued shares of Class A common stock upon a cashless warrant exercise by a non-employee. During the nine months ended September 30, 2020, SMC transferred its ownership of 242,681 shares of Class A common stock to ACM in exchange for the SMC Consideration. The 242,681 shares were cancelled during the nine months ended September 30, 2020. (Note 15) At September 30, 2021 and December 31, 2020, the number of shares of Class A common stock issued and outstanding was 17,798,740, and 16,896,693, respectively. At September 30, 2021 and December 31, 2020, the number of shares of Class B common stock issued and outstanding was 1,707,605 and 1,802,606, respectively.

REDEEMABLE NON-CONTROLLING INTE

REDEEMABLE NON-CONTROLLING INTERESTS	9 Months Ended
	Sep. 30, 2021
REDEEMABLE NON-CONTROLLING INTERESTS [Abstract]
REDEEMABLE NON-CONTROLLING INTERESTS	NOTE 19 – REDEEMABLE NON-CONTROLLING INTERESTS During the second quarter of 2020, the redemption feature of the private placement funding terminated and the aggregate proceeds of the funding therefore were reclassified from redeemable non-controlling interests to non-controlling interests. At September 30, 2020, the balance of redeemable non-controlling interest was nil The components of the change in the redeemable non-controlling interests for the nine months ended September 30, 2020 are presented in the following table: Balance at December 31, 2019 $ 60,162 Net income attributable to redeemable non-controlling interests 643 Effect of foreign currency translation gain attributable to redeemable non-controlling interests (847 ) Reclassification of redeemable non-controlling interest (59,958 ) Balance at September 30 2020 $ -

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	9 Months Ended
	Sep. 30, 2021
STOCK-BASED COMPENSATION [Abstract]
STOCK-BASED COMPENSATION	NOTE 20 – STOCK-BASED COMPENSATION In January 2020 ACM Shanghai adopted a 2019 Stock Option Incentive Plan (the “Subsidiary Stock Option Plan”) that provides for, among other incentives, the granting to officers, directors, employees of options to purchase shares of ACM Shanghai’s common stock. The fair value of the stock options granted is estimated at the date of grant based on the Black-Scholes option pricing model using assumptions generally consistent with those used for ACM’s stock options. Because ACM Shanghai shares are not publicly traded, the expected volatility is estimated with reference to the average historical volatility of a group of publicly traded companies that are believed to have similar characteristics to ACM Shanghai. ACM’s stock-based compensation consists of employee and non-employee awards issued under its 1998 Stock Option Plan, its 2016 Omnibus Incentive Plan, and as standalone options. ACM granted stock options to employees under the 2016 Omnibus Incentive Plan during the three and nine months ended September 30, 2021. The vesting condition may consist of a service period determined by the Board of Directors for a grant or certain performance conditions determined by the Board of Directors for a grant. The fair value of the stock options granted with service period based condition is estimated at the date of grant using the Black-Scholes option pricing model. The fair value of the stock options granted with market based condition is estimated at the date of grant using the Monte Carlo simulation model. The following table summarizes the components of stock-based compensation expense included in the consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Stock-Based Compensation Expense: Cost of revenue $ 108 $ 44 $ 289 $ 132 Sales and marketing expense 417 237 1,400 495 Research and development expense 293 193 801 568 General and administrative expense 460 2,305 1,333 3,128 $ 1,278 $ 2,779 $ 3,823 $ 4,323 Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Stock-based compensation expense by type: Employee stock purchase plan $ 1,179 $ 2,651 $ 3,481 $ 3,717 Non-employee stock purchase plan 12 44 82 356 Subsidiary option grants 87 84 260 250 $ 1,278 $ 2,779 $ 3,823 $ 4,323 The following table summarizes the Company’s employee share option activities during the nine months ended September 30, 2021: Number of Option Share Weighted Average Grant Date Fair Value Weighted Average Exercise Price Weighted Average Remaining Contractual Term Outstanding at December 31, 2020 3,191,411 $ 5.13 $ 12.73 7.13 years Granted 138,400 48.18 106.15 Exercised (443,683 ) 2.39 6.15 Forfeited/cancelled (33,404 ) 32.66 73.94 Outstanding at September 30, 2021 2,852,724 $ 7.32 $ 17.57 6.78 years Vested and exercisable at September 30, 2021 1,844,193 As of September 30, 2021 and December 31, 2020, $ and $ , respectively, of total unrecognized employee stock-based compensation expense, net of estimated forfeitures, related to stock-based awards for ACM were expected to be recognized over a weighted-average period of years and years, respectively. Total recognized compensation cost may be adjusted for future changes in estimated forfeitures. The fair value of options granted to employee with a is estimated on the grant date using the Black-Scholes valuation. Nine Months Ended September 30 2021 Fair value of common share(1) $ 82.75-111.98 Expected term in years(2) 5.50-6.25 Volatility(3) 48.53%-49.47 Risk-free interest rate(4) 1.00%-1.12% Expected dividend(5) 0 % (1) Equal to closing value on the grant date. (2) Expected term of share options is based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110. (3) Volatility is calculated based on the historical volatility of ACM’s comparable companies in the period equal to the expected term of each grant. (4) Risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant. (5) Expected dividend is assumed to be as ACM has no history or expectation of paying a dividend on its common stock. Non-employee Awards The following table summarizes the Company’s non-employee share option activities during the nine months ended September 30, 2021: Number of Option Shares Weighted Average Grant Date Fair Value Weighted Average Exercise Price Weighted Average Remaining Contractual Term Outstanding at December 31, 2020 836,038 $ 1.02 $ 3.07 4.92 Granted - - - Exercised (120,682 ) 1.23 4.29 Expired - - - Forfeited/cancelled (250 ) 0.30 0.75 Outstanding at September 30, 2021 715,106 $ 0.99 $ 2.86 4.15 Vested and exercisable at September 30, 2021 702,606 As of September 30, 2021 and December 31, 2020, $ and $ , respectively, of total unrecognized non-employee stock-based compensation expense, net of estimated forfeitures, related to stock-based awards were expected to be recognized over a weighted-average period of years and years, respectively. Total recognized compensation cost may be adjusted for future changes in estimated forfeitures. ACM Shanghai Option Grants The following table summarizes the ACM Shanghai employee stock option activities during the nine months ended September 30, 2021: Number of Option Shares in ACM Shanghai Weighted Average Grant Date Fair Value Weighted Average Exercise Price Weighted Average Remaining Contractual Term Outstanding at December 31, 2020 5,423,654 $ 0.23 $ 1.89 _ Granted - - - Exercised - - - Expired - - - Forfeited/cancelled (46,154 ) 0.24 2.01 Outstanding at September 30, 2021 5,377,500 $ 0.24 $ 2.01 2.76 years Vested and exercisable at September 30, 2021 - As of September 30, 2021 and December 31, 2020, $605 and $822, respectively, of total unrecognized non-employee stock-based compensation expense, net of estimated forfeitures, related to ACM Shanghai stock-based awards were expected to be recognized over a weighted-average period of 1.75 years and 2.50 years, respectively. Total recognized compensation cost may be adjusted for future changes in estimated forfeitures.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2021
INCOME TAXES [Abstract]
INCOME TAXES	NOTE 21 – INCOME TAXES Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carry-forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period during which such rates are enacted. The Company considers all available evidence to determine whether it is more likely than not that some portion or all of the deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become realizable. Management considers the scheduled reversal of deferred tax liabilities (including the impact of available carryback and carry-forward periods) and projected taxable income in assessing the realizability of deferred tax assets. In making such judgments, significant weight is given to evidence that can be objectively verified. As of each reporting date, management considers new evidence, both positive and negative, that could affect its view of the future realization of deferred tax assets. Prior to September 30, 2019, the Company had recorded a valuation allowance for the full amount of net deferred tax assets in the United States, as the realization of deferred tax assets was uncertain. Since September 30, 2019, the Company has not maintained a valuation allowance except for a partial valuation allowance on certain U.S. deferred tax assets. In order to recognize the remaining U.S. deferred tax assets that continue to be subject to a valuation allowance, the Company will need to generate sufficient U.S. taxable income in future periods before the expiration of the deferred tax assets governed by the tax code. ACM Shanghai has shown a three-year historical cumulative profit and has projections of future income. As a result, the Company does not maintain a valuation allowance. The Company accounts for uncertain tax positions in accordance with the authoritative guidance on income taxes under which the Company may only recognize or continue to recognize tax positions that meet a more likely than not threshold. The Company recognizes accrued interest and penalties related to unrecognized tax benefits as a component of the provision for income taxes. The Company’s effective tax rate differs from statutory rates of 21% for U.S. federal income tax purposes and 12.5% to 25% for Chinese income tax purposes due to the effects of the valuation allowance and certain permanent differences from book-tax differences. As a result, the Company recorded income tax benefit (expense) of $3,021 and $(416) during the nine months ended September 30, 2021 and 2020, respectively . As of September 30, 2021, the Company’s total unrecognized tax benefits were $570 of which $422 would affect the effective tax rate if recognized. The Company will recognize interest and penalties, when they occur, related to uncertain tax provisions as a component of tax expense. No interest or penalties were recognized for the nine months ended September 30, 2021. The Company files income tax returns in the United States and state and foreign jurisdictions. The federal, state and foreign income tax returns are under the statute of limitations subject to tax examinations for the tax years ended December 31, 2002 through December 31, 2020. To the extent the Company has tax attribute carry-forwards, the tax years in which the attribute was generated may still be adjusted upon examination by the U.S. Internal Revenue Service, state or foreign tax authorities to the extent utilized in a future period. The Company’s effective tax rate differs from statutory rates of for U.S. federal income tax purposes and to for Chinese income tax purposes due to the effects of the valuation allowance and certain permanent differences as it pertains to book-tax differences in the treatment of stock-based compensation and non-US research expenses. The Company’s PRC subsidiaries, ACM Shanghai, ACM Wuxi and ACM Shengwei, are liable for PRC corporate income taxes at the rates of , and respectively. Pursuant to the Corporate Income Tax Law of the PRC, ACM’s PRC subsidiaries generally would be liable for PRC corporate income taxes as a rate of . According to Guoshuihan No. an entity certified as an “advanced and new technology enterprise” is entitled to a preferential income tax rate of . ACM Shanghai was certified as an “advanced and new technology enterprise” in and again in and with an effective period of . In 2021, ACM Shanghai was certified as an eligible integrated circuit production enterprise and is entitled to a preferential income tax rate of from January 1, 2020 to December 31, 2022. ACM files income tax returns in the United States and state and foreign jurisdictions. Those federal, state and foreign income tax returns are under the statute of limitations subject to tax examinations for 2002 through 2020. To the extent ACM has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the U.S. Internal Revenue Service or state or foreign tax authorities to the extent utilized in a future period. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which enhances and simplifies various aspects of the income tax accounting guidance, including requirements such as the elimination of exceptions related to the approach for intra-period tax allocation, the methodology for calculating income taxes in an interim period, the recognition of deferred tax liabilities for outside basis differences, ownership changes in investments, and tax basis step-up in goodwill obtained in a transaction that is not a business combination. The guidance is effective for public companies for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. The impact of the adoption by the Company on its condensed consolidated financial statements and disclosures is immaterial. Income tax benefit (expense) was as follows: Three Months Ended September 30, Nine September 30 2021 2020 2021 2020 Total income tax benefit (expense) $ 266 $ 1,747 $ 3,021 $ (416 )

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2021
COMMITMENTS AND CONTINGENCIES [Abstract]
COMMITMENTS AND CONTINGENCIES	NOTE 22 – COMMITMENTS AND CONTINGENCIES The Company leases offices under non-cancelable operating lease agreements. See note for future minimum lease payments under non-cancelable operating lease agreements with initial terms of year or more. As of September the Company had of open capital commitments. Covenants in ACM Shengwei’s Grant Contract for State-owned Construction Land Use Right in Shanghai City with the China (Shanghai) Pilot Free Trade Zone Lingang Special Area Administration require, among other things, that ACM Shengwei pay liquidated damages in the event that (a) it does not make a total investment (including the costs of construction, fixtures, equipment and grant fees) of at least RMB 450.0 million ($63,400) or (b) within six years after the land use right is obtained, the Company does not (i) generate a minimum specified amount of annual sales of products manufactured on the granted land or (ii) pay to the PRC at least RMB 157.6 million ($22,000) in annual total taxes (including value-added taxes, corporate income tax, personal income taxes, urban maintenance and construction taxes, education surcharges, stamp taxes, and vehicle and shipping taxes) as a result of operations in connection with the granted land. As of September 30, 2021, the Company had paid in total $10,977 for its Lingang-related investments. In the normal course of business, the Company is subject to contingencies, including legal proceedings and environmental claims arising out of the normal course of businesses that relate to a wide range of matters, including among others, contracts breach liability. The Company records accruals for such contingencies based upon the assessment of the probability of occurrence and, where determinable, an estimate of the liability. Management may consider many factors in making these assessments including past history, scientific evidence and the specifics of each matter. Some of these contingencies involve claims that are subject to substantial uncertainties and unascertainable damages. The Company’s management has evaluated all such proceedings and claims that existed as of September 30, 2021 and December 31, 2020. In the opinion of management, no provision for liability nor disclosure was required as of September 30, 2021 related to any claim against the Company because: (a) there is not a reasonable possibility that a loss exceeding amounts already recognized (if any) may be incurred with respect to such claim; (b) a reasonably possible loss or range of loss cannot be estimated; or (c) such estimate is immaterial. As of September 30, 2021, the Company had one outstanding legal proceeding. On December 21, 2020, a p utative class action lawsuit against ACM and three of its officers was filed in the U.S. District Court for the Northern District of California under the caption Kain v. ACM Research, Inc., et al.

SUBSEQUENT EVENT

SUBSEQUENT EVENT	9 Months Ended
	Sep. 30, 2021
SUBSEQUENT EVENT [Abstract]
SUBSEQUENT EVENT	NOTE 23 – SUBSEQUENT EVENT On November 1, 2021, ACM announced that the Shanghai Stock Exchange had published ACM Shanghai's updated STAR IPO prospectus and STAR IPO timetable on its website. On November 4, 2021, ACM advised that the Shanghai Stock Exchange had announced the pricing of the STAR IPO shares of ACM Shanghai. In the IPO, ACM Shanghai proposes to issue 43,355,753 shares, which will represent 10% of the total 433,557,100 shares to be outstanding after the IPO. Of the shares issued in the IPO, 7,699,357 shares will be issued via direct placement to private equity investors. The proposed offering price of shares in the IPO is RMB 85.00 per share, which, if completed, would result in total gross proceeds of the IPO to ACM Shanghai of approximately RMB 3.685 billion (approximately $575,000 as of November 4, 2021). After the IPO, ACM will own approximately 82.5% of the outstanding shares of ACM Shanghai.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The Company’s condensed consolidated financial statements include the accounts of ACM and its subsidiaries, including ACM Shanghai and its subsidiaries, which include ACM Wuxi, ACM Shengwei and CleanChip (the subsidiaries of which include ACM California and ACM Korea). ACM’s subsidiaries are those entities in which ACM, directly or indirectly, controls a majority of the voting power. All significant intercompany transactions and balances have been eliminated upon consolidation. The accompanying condensed consolidated financial statements of the Company have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and the rules and regulations of the Securities and Exchange Commission for reporting on Form -Q. Accordingly, they do not include all the information and footnotes required by GAAP for complete financial statements. The accompanying condensed consolidated financial statements should be read in conjunction with the historical consolidated financial statements of the Company for the year ended December included in ACM’s Annual Report on Form -K for the year ended December . The accompanying condensed consolidated balance sheet as of September condensed consolidated statements of operations and comprehensive income for the and months ended September and condensed consolidated statements of changes in stockholders’ equity for the and months ended September and and condensed consolidated statements of cash flows for the months ended September and are unaudited. In the opinion of management, these unaudited condensed consolidated financial statements of the Company reflect all adjustments that are necessary for a fair presentation of the Company’s financial position and results of operations. Such adjustments are of a normal recurring nature, unless otherwise noted. The balance sheet as of September and the results of operations for the and months ended September are not necessarily indicative of the results to be expected for any future period.
COVID-19 Assessment	COVID-19 Assessment The outbreak of COVID- the coronavirus, has grown both in the United States and globally, and related government and private sector responsive actions have adversely affected the Company’s business operations. In December a series of emergency quarantine measures taken by the PRC government disrupted domestic business activities during the weeks after the initial outbreak of COVID- Since that time, an increasing number of countries, including the United States, have imposed restrictions on travel to and from the PRC and elsewhere, as well as general movement restrictions, business closures and other measures imposed to slow the spread of COVID- The situation continues to develop, and it is impossible to predict the effect and ultimate impact of the COVID- outbreak on the Company’s business operations and results. While the quarantine, social distancing and other regulatory measures instituted or recommended in response to COVID- are expected to be temporary, the duration of the business disruptions and related financial impact cannot be estimated at this time. The COVID- outbreak has been declared a worldwide health pandemic that could adversely affect the economies and financial markets of many countries, resulting in an economic downturn and changes in global economic policy that could reduce demand for the Company’s products and its customers’ chips and have a material adverse impact on the Company’s business, operating results and financial condition. Through September the Company had not experienced a significant negative impact of COVID- on its operations, capital and financial resources, including overall liquidity position. The Company continues to monitor the impact of the COVID-19 pandemic on all aspects of its business. The Company conducts substantially all of its product development, manufacturing, support and services in the PRC, and those activities have been directly impacted by the COVID- outbreak and related restrictions on transportation and public appearances. In February ACM Shanghai’s headquarters were closed for an additional beyond the normal Lunar New Year Holiday in accordance with Shanghai government restrictions related to the outbreak. The Company cannot assure that further closures or reductions of its PRC operations or production may not be necessary in upcoming months as the result of business interruptions arising from protective measures being taken by the PRC and other governmental agencies or of other consequences of the COVID- outbreak. The Company’s corporate headquarters are located in Alameda County in the San Francisco Bay Area of California. The effects of any future actions by the State of California, the San Francisco Department of Public Health, health officers of the San Francisco Bay Area counties or other local health officials that intended to mitigate the COVID-19 pandemic may negatively impact productivity, disrupt the business of the Company and delay timelines, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on the Company’s ability to conduct its business in the ordinary course. The prolonged and broad-based shift to a remote working environment continues to create inherent productivity, connectivity, and oversight challenges and could affect our ability to enhance, develop and support existing products and services, detect and prevent spam and problematic content, hold product sales and marketing events, and generate new sales leads, among others. In addition, the changed environment under which the Company is operating could have an effect on its internal controls over financial reporting as well as the Company’s ability to meet a number of its compliance requirements in a timely or quality manner. Additional and/or extended, governmental lockdowns, restrictions or new regulations could significantly impact the ability of our employees and vendors to work productively. Governmental restrictions have been globally inconsistent and it remains unclear when a return to worksite locations or travel will be permitted or what restrictions will be in place in those environments. As the Company continues to return its workforce in more office locations in it may experience increased costs as it prepares its facilities for a safe return to work environment and experiment with hybrid work models, in addition to potential effects on its ability to compete effectively and maintain its corporate culture. Extended periods of interruption to the Company’s corporate, development or manufacturing facilities due to the COVID- outbreak could cause the Company to lose revenue and market share, which would depress its financial performance and could be difficult to recapture. The Company’s business may also be harmed if travel to or from the PRC or the United States continues to be restricted or inadvisable or if members of management and other employees are absent because they contract the coronavirus, they elect not to come to work due to the illness affecting others in the Company’s office or laboratory facilities, or they are subject to quarantines or other governmentally imposed restrictions.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the balance sheet date and the reported revenues and expenses during the reported period in the consolidated financial statements and accompanying notes. The Company’s significant accounting estimates and assumptions include, but are not limited to, those used for the valuation and recognition of fair value of trading securities, stock-based compensation arrangements and warrant liability, realization of deferred tax assets, assessment for impairment of long-lived assets, allowance for doubtful accounts, inventory valuation for excess and obsolete inventories, lower of cost and market value or net realizable value of inventories, depreciable lives of property and equipment and useful life of intangible assets. Management evaluates these estimates and assumptions on a regular basis. Actual results could differ from those estimates and assumptions.
Basic and Diluted Net Income per Common Share	Basic and Diluted Net Income per Common Share Basic and diluted net income per common share are calculated as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net income $ 11,150 $ 10,020 $ 24,306 $ 12,479 Less: Net income attributable to non-controlling interests and redeemable non-controlling interests 995 1,393 2,114 2,228 Net income available to common stockholders, basic and diluted $ 10,155 $ 8,627 $ 22,192 $ 10,251 Weighted average shares outstanding, basic 19,422,546 18,201,943 19,113,353 18,124,665 Effect of dilutive securities 2,619,970 3,353,353 2,616,987 3,132,996 Weighted average shares outstanding, diluted 22,042,516 21,555,296 21,730,340 21,257,661 Net income per common share: Basic $ 0.52 $ 0.47 $ 1.16 $ 0.57 Diluted $ 0.46 $ 0.40 $ 1.02 $ 0.48 ACM has been authorized to issue Class A and Class B common stock since redomesticating in Delaware in November The classes of common stock are substantially identical in all material respects, except for voting rights. Since ACM did not declare any dividends during the and nine months ended September and the net income per common share attributable to each class is the same under the “ -class” method. As such, the classes of common stock have been presented on a combined basis in the condensed consolidated statements of operations and comprehensive income and in the above computation of net income per common share. Diluted net income per common share reflects the potential dilution from securities, including stock options and issued warrants, that could share in ACM’s earnings. Certain potential dilutive securities were excluded from the net income per share calculation because the impact would be anti-dilutive. ACM’s potential dilutive securities consist of warrants and stock options for the months ended September ’
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to credit risk consist principally of cash and cash equivalents and accounts receivable. The Company deposits and invests its cash with financial institutions that management believes are creditworthy. The Company is potentially subject to concentrations of credit risks in its accounts receivable. For the nine months ended September
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2019 - 12, Income Taxes (Topic 740) : Simplifying the Accounting for Income Taxes . ASU 2019 - 12 simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740. It also improves consistent application of and simplifies GAAP for other areas of Topic 740 by clarifying and amending existing guidance. The Company adopted ASU 2019 - 12 on January 1, 2021. The adoption of ASU 2019 - 12 did not have a material impact on the Company’s condensed consolidated financial statements. In March the FASB issued ASU No. - Reference Rate Reform (Topic : Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU - provide optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The Company adopted ASU - on January The adoption of ASU - did not have a material impact on the Company’s condensed consolidated financial statements. Recent Accounting Pronouncements Not Yet Adopted In June the FASB issued ASU - Financial Instruments-Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments . ASU - replaced the pre-existing incurred loss impairment methodology with a methodology that reflects expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. ASU - requires use of a forward-looking expected credit loss model for accounts receivables, loans and other financial instruments. ASU - is effective for fiscal years beginning after December with early adoption permitted. In October the FASB issued ASU - Financial Instruments – Credit Losses (Topic 326) , Derivatives and Hedging (Topic 815) and Leases (Topic 842) , which defers the effective date for public filers that are considered small reporting companies (“SRC”) as defined by the U.S. Securities and Exchange Commission (“SEC”) to fiscal years beginning after December including interim periods within those fiscal years. Since the Company was eligible to be an SRC based on its SRC determination as of November (which is the issuance date of ASU - in accordance with SEC regulations, the Company will adopt the standards for the year beginning January Adoption of the standard requires using a modified retrospective approach through a cumulative-effect adjustment to retained earnings as of the effective date to align existing credit loss methodology with the new standard. The Company is evaluating the impact of this standard on its consolidated financial statements, including accounting policies, processes and systems and expects the standard will have a minor impact on its consolidated financial statements.

DESCRIPTION OF BUSINESS (Tables

DESCRIPTION OF BUSINESS (Tables)	9 Months Ended
	Sep. 30, 2021
DESCRIPTION OF BUSINESS [Abstract]
Direct or Indirect Interests of Subsidiaries	The Company has direct or indirect interests in the following subsidiaries: Effective interest held as at Name of subsidiaries Place and date of incorporation September 30, 2021 December 31, 2020 ACM Research (Shanghai), Inc. PRC, May 2005 91.7 % 91.7 % ACM Research (Wuxi), Inc. PRC, July 2011 91.7 % 91.7 % CleanChip Technologies Limited Hong Kong, September 2017 91.7 % 91.7 % ACM Research Korea CO., LTD. Korea, December 2017 91.7 % 91.7 % Shengwei Research (Shanghai), Inc. PRC, March 2019 91.7 % 91.7 % ACM Research (CA), Inc. USA, April 2019 91.7 % 91.7 % ACM Research (Cayman), Inc. Cayman Islands, April 2019 100.0 % 100.0 % ACM Research (Singapore) PTE, Ltd. Singapore, August 2021 100.0 % 0.0 %

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	9 Months Ended
	Sep. 30, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Basic and Diluted Net Income per Common Share	Basic and diluted net income per common share are calculated as follows: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net income $ 11,150 $ 10,020 $ 24,306 $ 12,479 Less: Net income attributable to non-controlling interests and redeemable non-controlling interests 995 1,393 2,114 2,228 Net income available to common stockholders, basic and diluted $ 10,155 $ 8,627 $ 22,192 $ 10,251 Weighted average shares outstanding, basic 19,422,546 18,201,943 19,113,353 18,124,665 Effect of dilutive securities 2,619,970 3,353,353 2,616,987 3,132,996 Weighted average shares outstanding, diluted 22,042,516 21,555,296 21,730,340 21,257,661 Net income per common share: Basic $ 0.52 $ 0.47 $ 1.16 $ 0.57 Diluted $ 0.46 $ 0.40 $ 1.02 $ 0.48

REVENUE FROM CONTRACTS WITH C_2

REVENUE FROM CONTRACTS WITH CUSTOMERS (Tables)	9 Months Ended
	Sep. 30, 2021
REVENUE FROM CONTRACTS WITH CUSTOMERS [Abstract]
Disaggregated Revenue Information	The Company assesses revenues based upon the nature or type of goods or services it provides and the geographic location of the related businesses. The following tables present disaggregated revenue information: Three Months Ended , Nine September 30 2021 2020 2021 2020 Single wafer cleaning, Tahoe and semi-critical cleaning equipment $ 49,448 $ 38,344 $ 127,322 $ 94,468 ECP (front-end and packaging), furnace and other technologies 8,200 4,850 13,750 9,340 Advanced packaging (excluding ECP), services & spares 9,365 4,471 23,537 7,254 Total Revenue By Product Category $ 67,013 $ 47,665 $ 164,609 $ 111,062 Wet cleaning and other front-end processing tools $ 49,448 $ 38,344 $ 127,322 $ 98,958 Advanced packaging, other processing tools, services and spares 17,565 9,321 37,287 12,104 Total Revenue Fron t-end $ 67,013 $ 47,665 $ 164,609 $ 111,062 Three Months Ended , Nine September 30 2021 2020 2021 2020 Mainland China $ 66,887 $ 46,881 $ 164,319 $ 110,174 Other Regions 126 784 290 888 $ 67,013 $ 47,665 $ 164,609 $ 111,062

ACCOUNTS RECEIVABLE (Tables)

ACCOUNTS RECEIVABLE (Tables)	9 Months Ended
	Sep. 30, 2021
ACCOUNTS RECEIVABLE [Abstract]
Accounts Receivable	A t September 30, 2021 and December 31, 2020 accounts receivable consisted of the followin September 30, 2021 December 31, 2020 Accounts receivable $ 84,787 $ 56,441 Less: Allowance for doubtful accounts - - Total $ 84,787 $ 56,441

INVENTORIES (Tables)

INVENTORIES (Tables)	9 Months Ended
	Sep. 30, 2021
INVENTORIES [Abstract]
Inventory	At September 30, 2021 and December 31, 2020 inventory consisted of the following: September 30, 2021 December 31, 2020 Raw materials $ 65,029 $ 32,391 Work in process 29,682 23,871 Finished goods 81,898 32,377 Total inventory $ 176,609 $ 88,639

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT, NET (Tables)	9 Months Ended
	Sep. 30, 2021
PROPERTY, PLANT AND EQUIPMENT, NET [Abstract]
Property, Plant and Equipment	At September 30, 2021 and December 31, 2020, property, plant and equipment consisted of the following: September 30, 2021 December 31, 2020 Manufacturing equipment $ 6,992 $ 5,966 Office equipment 1,642 1,047 Transportation equipment 214 216 Leasehold improvement 2,932 2,398 Total cost 11,780 9,627 Less: Total accumulated depreciation (5,120 ) (3,745 ) Construction in progress 3,345 2,310 Total property, plant and equipment, net $ 10,005 $ 8,192

LAND USE RIGHT, NET (Tables)

LAND USE RIGHT, NET (Tables)	9 Months Ended
	Sep. 30, 2021
LAND USE RIGHT, NET [Abstract]
Land Use Rights	A summary of land use right is as follows: September 30, 2021 December 31, 2020 Land use right purchase amount $ 9,801 $ 9,744 Less: Accumulated amortization (245 ) (98 ) Land use right, net $ 9,556 $ 9,646
Remaining Amortization of Land Use Right	The remaining amortization of land use right for each of the five succeeding years is as follows: Year ending December 31, 2021 $ 49 2022 196 2023 196 2024 196 2025 196

OTHER LONG-TERM ASSETS (Tables)

OTHER LONG-TERM ASSETS (Tables)	9 Months Ended
	Sep. 30, 2021
OTHER LONG-TERM ASSETS [Abstract]
Other Long-term Assets	At September 30, 2021 and December 31, 2020, other long-term assets consisted of the following: September 30, 2021 December 31, 2020 Prepayment for property - Lingang $ 40,433 $ 39,450 Prepayment for property, plant and equipment and other non-current assets 1,692 - Prepayment for property - lease deposit 422 - Security deposit for land use right 760 756 Others 936 290 Total other long-term assets $ 44,243 $ 40,496

SHORT-TERM BORROWINGS (Tables)

SHORT-TERM BORROWINGS (Tables)	9 Months Ended
	Sep. 30, 2021
SHORT-TERM BORROWINGS [Abstract]
Short-Term Borrowings	At September 30, 2021 and December 31, 2020, short-term borrowings consisted of the following: September 30, 2021 December 31, 2020 Line of credit up to RMB 80,000 1)due on April 1, 2021 with an annual interest rate of 4.70 March 23, 2021 $ - $ 4,599 2)due on June 27, 2021 with an annual interest rate of 4.25 June 28, 2021 - 1,380 3)due on April 29, 2021 with an annual interest rate of 2.80 March 23, 2021 - 820 4)due on June 27, 2021 with an annual interest rate of 2.70 June 25, 2021 - 2,080 Line of credit up to RMB 20,000 1)due on April 12, 2021 with an annual interest rate of 4.65% and fully repaid on April 12, 2021. - 1,533 2)due on May 24, 2021 with an annual interest rate of 3.65% and fully repaid on May 24, 2021. - 1,533 Line of credit up to RMB 70,000 from Bank of Shanghai Pudong Branch, 1)due on May 27, 2021 with an annual interest rate of 4.68%. *2 and fully repaid on May 27, 2021. - 2,575 2)due on June 27, 2021 with an annual interest rate of 4.68%. *2 and fully repaid on March 29, 2021. - 1,380 3)due on May 28, 2021 with an annual interest rate of 3.48%. *2 and fully repaid on May 28, 2021. - 2,442 4)due on June 7, 2021 with an annual interest rate of 3.50%. *2 and fully repaid on June 7, 2021. - 1,521 5)due on June 16, 2021 with an annual interest rate of 3.50%. *2 and fully repaid on June 16, 2021. - 1,838 Line of credit up to RMB 80,000 from China Merchants Bank, 1)due on August 10, 2021 with annual interest rate of 3.85% and fully repaid on August 10, 2021. - 1,380 2)due on August 25, 2021 with annual interest rate of 3.85% and fully repaid on August 25, 2021. - 3,066 3)due on February 1, 2022 with annual interest rate of 3.85%. 1,388 - 4)due on May 26, 2022 with annual interest rate of 3.9%. 1,388 - 5)due on February 2, 2022 with annual interest rate of 3.95%. 1,465 - 6)due on February 2, 2022 with annual interest rate of 3.95%. 1,465 - 7)due on February 2, 2022 with annual interest rate of 3.95%. 1,387 - Line of credit up to RMB 100,000 from Bank of Shanghai Pudong Branch, 1)due on June 7, 2022 with an annual interest rate of 2.7%. *3 4,618 - Line of credit up to RMB 40,000 from Bank of China, 1)due on June 15, 2022 with an annual interest rate of 3.86%. 3,068 - Line of credit up to KRW 500,000 from Industrial Bank of Korea (IBK) 1)due on July 11, 2022 with an annual interest rate of 5.40%. *4 422 - Total $ 15,201 $ 26,147 *1 Guaranteed by ACM’s Chief Executive Officer *2 Guaranteed by ACM’s Chief Executive Officer and CleanChip *3 Guaranteed by CleanChip *4 Guaranteed by ACM Korea’s Chief Executive Officer

OTHER PAYABLE AND ACCRUED EXP_2

OTHER PAYABLE AND ACCRUED EXPENSES (Tables)	9 Months Ended
	Sep. 30, 2021
OTHER PAYABLE AND ACCRUED EXPENSES [Abstract]
Other Payable and Accrued Expenses	At September 30, 2021 and December 31, 2020, other payable and accrued expenses consisted of the following: September 30, 2021 December 31, 2020 Accrued commissions 10,527 7,127 Accrued warranty 5,117 3,975 Accrued payroll 3,492 3,068 Accrued professional fees 40 384 Accrued machine testing fees 1,825 1,595 Others 4,949 2,656 Total $ 25,950 $ 18,805

LEASES (Tables)

LEASES (Tables)	9 Months Ended
	Sep. 30, 2021
LEASES [Abstract]
Components of Lease Expense	The components of lease expense were as follows: Three Months Ended September 30, Nine September 30 2021 2020 2021 2020 Operating lease cost $ 632 $ 384 $ 1,807 $ 1,139 Short-term lease cost 105 73 258 170 Lease cost $ 737 $ 457 $ 2,065 $ 1,309
Supplemental Cash Flow Information Related to Operating Leases	Supplemental cash flow information related to operating leases was as follows for the three and nine months ended September 30, 2021 and 2020 Three Months Ended September 30, Nine September 30 2021 2020 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash outflow from operating leases $ 737 $ 457 $ 2,065 $ 1,309
Maturities of Lease Liabilities for Operating Leases	Maturities of lease liabilities for all operating leases were as follows as of September 30, 2021 December 31, 2021 631 2022 2,292 2023 1,020 2024 914 2025 19 Total lease payments 4,876 Less: Interest (277 ) Present value of lease liabilities $ 4,599
Weighted Average Remaining Lease Terms and Discount Rates for Operating Leases	The weighted average remaining lease terms and discount rates for all operating leases were as follows as of September 30 and December : September 30, 2021 December 31, 2020 Remaining lease term and discount rate: Weighted average remaining lease term (years) 1.50 2.11 Weighted average discount rate 4.58 % 5.14 %

LONG-TERM BORROWINGS (Tables)

LONG-TERM BORROWINGS (Tables)	9 Months Ended
	Sep. 30, 2021
LONG-TERM BORROWINGS [Abstract]
Long-Term Borrowings	At September 30 and December long-term borrowings consisted of the following: September 30, 2021 December 31, 2020 Loan from China Merchants Bank $ 18,492 $ 19,570 Loans from Bank of China $ 6,939 - Less: Current portion (2,351 ) (1,591 ) $ 23,080 $ 17,979
Principal Payments for Outstanding Long-Term Loan	Scheduled principal payments for the outstanding long-term loan as of September 30 are as follows: Year ending December 31 2021 $ 484 2022 2,370 2023 2,450 2024 7,313 2025 and onwards 12,814 $ 25,431

OTHER LONG-TERM LIABILITIES (Ta

OTHER LONG-TERM LIABILITIES (Tables)	9 Months Ended
	Sep. 30, 2021
OTHER LONG-TERM LIABILITIES [Abstract]
Other Long-Term Liabilities	Other long-term liabilities represent government subsidies received from PRC governmental authorities for development and commercialization of certain technology but not yet recognized. As of September 30 and December other long-term liabilities consisted of the following unearned government subsidies: September 30, 2021 December 31, 2020 Subsidies to Stress Free Polishing project, commenced in 2008 and 2017 $ 949 $ 1,266 Subsidies to Electro Copper Plating project, commenced in 2014 901 2,156 Subsidies to Polytetrafluoroethylene, commenced in 2018 - 130 Subsidies to Tahoe-Single Bench Clean, commenced in 2020 185 1,544 Subsidies to Backside Clean-YMTC National Project, commenced in 2020 2,779 2,591 Other 489 347 Total $ 5,303 $ 8,034

LONG-TERM INVESTMENT (Tables)

LONG-TERM INVESTMENT (Tables)	9 Months Ended
	Sep. 30, 2021
LONG-TERM INVESTMENT [Abstract]
Components of Long-Term Investment	The Company treats the equity investment in the consolidated financial statements under the equity method. Under the equity method, the investment is initially recorded at cost, adjusted for any excess of the Company’s share of the incorporated-date fair values of the investee’s identifiable net assets over the cost of the investment (if any). Thereafter, the investment is adjusted for the post incorporation change in the Company’s share of the investee’s net assets and any impairment loss relating to the investment. September 30, 2021 December 31, 2020 Ninebell $ 2,713 $ 1,666 Shengyi 186 134 Hefei Shixi 4,509 4,540 Total $ 7,408 $ 6,340

FINANCIAL LIABILITY CARRIED A_2

FINANCIAL LIABILITY CARRIED AT FAIR VALUE (Tables)	9 Months Ended
	Sep. 30, 2021
FINANCIAL LIABILITY CARRIED AT FAIR VALUE [Abstract]
Assumptions Used to Determine Fair Value of Warrants	The 2020 Warrant was initially measured at fair value at the issuance date and classified as equity permanently in accordance with ASC 815. The fair value of the 2020 Warrant amounted to $21,679, based on the grant date using the Black-Scholes valuation model with the following assumptions: July 29, 2020 Fair value of common share(1) $ 89.28 Expected term in years(2) 3.42 Volatility(3) 47.42 % Risk-free interest rate(4) 0.15 % Expected dividend(5) 0 % (1) Fair value of Class A common stock was the closing market price of the Class A common stock on July 29, 2020. (2) Expected term of share options was based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110. (3) Volatility was calculated based on the historical volatility of the stock of companies comparable to ACM in the period equal to the expected term of each grant. (4) Risk-free interest rate was based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant. (5) Expected dividend was assumed to be 0%, as ACM had no history or expectation of paying a dividend on its common stock.

TRADING SECURITIES (Tables)

TRADING SECURITIES (Tables)	9 Months Ended
	Sep. 30, 2021
TRADING SECURITIES [Abstract]
Components of Trading Securities	The components of trading securities were as follows: September 30, 2021 December 31, 2020 Trading securities listed in Shanghai Stock Exchange Cost $ 15,108 $ 15,020 Market value $ 30,219 $ 28,239

RELATED PARTY BALANCES AND TR_2

RELATED PARTY BALANCES AND TRANSACTIONS (Tables)	9 Months Ended
	Sep. 30, 2021
RELATED PARTY BALANCES AND TRANSACTIONS [Abstract]
Related Party Balances and Transactions	Prepaid expenses September 30, 2021 December 31, 2020 Ninebell $ 2,192 $ 1,607 Accounts payable September 30, 2021 December 31, 2020 Ninebell $ 6,340 $ 2,898 Shengyi 1,920 1,195 Total $ 8,260 $ 4,093 Three Months Ended , Nine Months Ended , Purchase of materials 2021 2020 2021 2020 Ninebell $ 7,455 $ 4,029 $ 21,833 $ 9,552 Shengyi 1,108 599 1,753 1,113 Total $ 8,563 $ 4,628 $ 23,586 $ 10,665 Three Months Ended September 30, Nine Months Ended September 30, Service fee charged by 2021 2020 2021 2020 Shengyi $ 144 $ 14 $ 403 $ 204 Ninebell - 22 - 22 Total $ 144 $ 36 $ 403 $ 226

REDEEMABLE NON-CONTROLLING IN_2

REDEEMABLE NON-CONTROLLING INTERESTS (Tables)	9 Months Ended
	Sep. 30, 2021
REDEEMABLE NON-CONTROLLING INTERESTS [Abstract]
Components of Change in Redeemable Non-controlling Interests	The components of the change in the redeemable non-controlling interests for the nine months ended September 30, 2020 are presented in the following table: Balance at December 31, 2019 $ 60,162 Net income attributable to redeemable non-controlling interests 643 Effect of foreign currency translation gain attributable to redeemable non-controlling interests (847 ) Reclassification of redeemable non-controlling interest (59,958 ) Balance at September 30 2020 $ -

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	9 Months Ended
	Sep. 30, 2021
Stock-Based Compensation [Abstract]
Components of Stock-based Compensation Expense	The following table summarizes the components of stock-based compensation expense included in the consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Stock-Based Compensation Expense: Cost of revenue $ 108 $ 44 $ 289 $ 132 Sales and marketing expense 417 237 1,400 495 Research and development expense 293 193 801 568 General and administrative expense 460 2,305 1,333 3,128 $ 1,278 $ 2,779 $ 3,823 $ 4,323 Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Stock-based compensation expense by type: Employee stock purchase plan $ 1,179 $ 2,651 $ 3,481 $ 3,717 Non-employee stock purchase plan 12 44 82 356 Subsidiary option grants 87 84 260 250 $ 1,278 $ 2,779 $ 3,823 $ 4,323
Assumptions Used to Determine Fair Value of Share Options Granted	The fair value of options granted to employee with a is estimated on the grant date using the Black-Scholes valuation. Nine Months Ended September 30 2021 Fair value of common share(1) $ 82.75-111.98 Expected term in years(2) 5.50-6.25 Volatility(3) 48.53%-49.47 Risk-free interest rate(4) 1.00%-1.12% Expected dividend(5) 0 % (1) Equal to closing value on the grant date. (2) Expected term of share options is based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110. (3) Volatility is calculated based on the historical volatility of ACM’s comparable companies in the period equal to the expected term of each grant. (4) Risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant. (5) Expected dividend is assumed to be as ACM has no history or expectation of paying a dividend on its common stock.
Employee Share Option [Member]
Stock-Based Compensation [Abstract]
Summary of Share Option Activities	The following table summarizes the ACM Shanghai employee stock option activities during the nine months ended September 30, 2021: Number of Option Shares in ACM Shanghai Weighted Average Grant Date Fair Value Weighted Average Exercise Price Weighted Average Remaining Contractual Term Outstanding at December 31, 2020 5,423,654 $ 0.23 $ 1.89 _ Granted - - - Exercised - - - Expired - - - Forfeited/cancelled (46,154 ) 0.24 2.01 Outstanding at September 30, 2021 5,377,500 $ 0.24 $ 2.01 2.76 years Vested and exercisable at September 30, 2021 -
Employee Share Option [Member] | ACM Shanghai [Member]
Stock-Based Compensation [Abstract]
Summary of Share Option Activities	The following table summarizes the Company’s employee share option activities during the nine months ended September 30, 2021: Number of Option Share Weighted Average Grant Date Fair Value Weighted Average Exercise Price Weighted Average Remaining Contractual Term Outstanding at December 31, 2020 3,191,411 $ 5.13 $ 12.73 7.13 years Granted 138,400 48.18 106.15 Exercised (443,683 ) 2.39 6.15 Forfeited/cancelled (33,404 ) 32.66 73.94 Outstanding at September 30, 2021 2,852,724 $ 7.32 $ 17.57 6.78 years Vested and exercisable at September 30, 2021 1,844,193
Non-Employee Stock Option [Member]
Stock-Based Compensation [Abstract]
Summary of Share Option Activities	The following table summarizes the Company’s non-employee share option activities during the nine months ended September 30, 2021: Number of Option Shares Weighted Average Grant Date Fair Value Weighted Average Exercise Price Weighted Average Remaining Contractual Term Outstanding at December 31, 2020 836,038 $ 1.02 $ 3.07 4.92 Granted - - - Exercised (120,682 ) 1.23 4.29 Expired - - - Forfeited/cancelled (250 ) 0.30 0.75 Outstanding at September 30, 2021 715,106 $ 0.99 $ 2.86 4.15 Vested and exercisable at September 30, 2021 702,606

INCOME TAXES (Tables)

INCOME TAXES (Tables)	9 Months Ended
	Sep. 30, 2021
INCOME TAXES [Abstract]
Income Tax Benefit (Expense)	Income tax benefit (expense) was as follows: Three Months Ended September 30, Nine September 30 2021 2020 2021 2020 Total income tax benefit (expense) $ 266 $ 1,747 $ 3,021 $ (416 )

DESCRIPTION OF BUSINESS (Detail

DESCRIPTION OF BUSINESS (Details) $ in Thousands	Sep. 13, 2017	Sep. 30, 2021	Dec. 31, 2019USD ($)	Dec. 31, 2020	Sep. 30, 2020	Nov. 08, 2017	Aug. 31, 2017
Class A Common Stock [Member]
Description of Business [Abstract]
Reverse stock split	0.33
Class B Common Stock [Member]
Description of Business [Abstract]
Reverse stock split	0.33
ACM Research (Shanghai), Inc. [Member]
Description of Business [Abstract]
Purchase of equity interest percentage					8.30%	18.36%	18.77%
Term to complete listing of shares		3 years
Name of subsidiaries		ACM Research (Shanghai), Inc.
Place and date of incorporation		PRC, May 2005
Effective interest held as at		91.70%		91.70%
ACM Research (Wuxi), Inc. [Member]
Description of Business [Abstract]
Name of subsidiaries		ACM Research (Wuxi), Inc.
Place and date of incorporation		PRC, July 2011
Effective interest held as at		91.70%		91.70%
CleanChip Technologies Limited [Member]
Description of Business [Abstract]
Proceeds from sale of interest in subsidiary			$ 3,500
Name of subsidiaries		CleanChip Technologies Limited
Place and date of incorporation		Hong Kong, September 2017
Effective interest held as at		91.70%		91.70%
ACM Research Korea CO., LTD [Member]
Description of Business [Abstract]
Name of subsidiaries		ACM Research Korea CO., LTD.
Place and date of incorporation		Korea, December 2017
Effective interest held as at		91.70%		91.70%
Shengwei Research (Shanghai), Inc. [Member]
Description of Business [Abstract]
Purchase of equity interest percentage					91.70%
Name of subsidiaries		Shengwei Research (Shanghai), Inc.
Place and date of incorporation		PRC, March 2019
Effective interest held as at		91.70%		91.70%
ACM Research (CA), Inc. [Member]
Description of Business [Abstract]
Name of subsidiaries		ACM Research (CA), Inc.
Place and date of incorporation		USA, April 2019
Effective interest held as at		91.70%		91.70%
ACM Research (Cayman), Inc. [Member]
Description of Business [Abstract]
Name of subsidiaries		ACM Research (Cayman), Inc.
Place and date of incorporation		Cayman Islands, April 2019
Effective interest held as at		100.00%		100.00%
ACM Research (Singapore) PTE, Ltd. [Member]
Description of Business [Abstract]
Name of subsidiaries		ACM Research (Singapore) PTE, Ltd.
Place and date of incorporation		Singapore, August 2021
Effective interest held as at		100.00%		0.00%

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, COVID-19 Assessment (Details)	1 Months Ended
	Feb. 29, 2020
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Number of days headquarters closed	6 days

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Basic and Diluted Net Income per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator [Abstract]
Net income	$ 11,150	$ 10,020	$ 24,306	$ 12,479
Less: Net income attributable to non-controlling interests and redeemable non-controlling interests	995	1,393	2,114	2,228
Net income available to common stockholders, basic and diluted	$ 10,155	$ 8,627	$ 22,192	$ 10,251
Weighted average shares outstanding, basic (in shares)	19,422,546	18,201,943	19,113,353	18,124,665
Effect of dilutive securities (in shares)	2,619,970	3,353,353	2,616,987	3,132,996
Weighted average shares outstanding, diluted (in shares)	22,042,516	21,555,296	21,730,340	21,257,661
Net income per common share [Abstract]
Basic (in dollars per share)	$ 0.52	$ 0.47	$ 1.16	$ 0.57
Diluted (in dollars per share)	$ 0.46	$ 0.40	$ 1.02	$ 0.48

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Concentration of Credit Risk (Details) - Customer Concentration Risk [Member] - Three Customers [Member] - Customer	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenue Benchmark [Member]
Concentration of Credit Risk [Abstract]
Number of major customers	3	3	3	3
Concentration of credit risk	77.10%	72.10%	65.60%	79.80%
Accounts Receivable [Member]
Concentration of Credit Risk [Abstract]
Number of major customers			3		3
Concentration of credit risk			73.80%		75.80%

REVENUE FROM CONTRACTS WITH C_3

REVENUE FROM CONTRACTS WITH CUSTOMERS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregated Revenue Information [Abstract]
Revenue	$ 67,013	$ 47,665	$ 164,609	$ 111,062
Mainland China [Member]
Disaggregated Revenue Information [Abstract]
Revenue	66,887	46,881	164,319	110,174
Oher Regions [Member]
Disaggregated Revenue Information [Abstract]
Revenue	126	784	290	888
Single Wafer Cleaning, Tahoe and Semi-Critical Cleaning Equipment [Member]
Disaggregated Revenue Information [Abstract]
Revenue	49,448	38,344	127,322	94,468
ECP (Front-end and Packaging), Furnace and Other Technologies [Member]
Disaggregated Revenue Information [Abstract]
Revenue	8,200	4,850	13,750	9,340
Advanced Packaging (Excluding ECP), Services & Spares [Member]
Disaggregated Revenue Information [Abstract]
Revenue	9,365	4,471	23,537	7,254
Wet Cleaning and Other Front-end Processing Tools [Member]
Disaggregated Revenue Information [Abstract]
Revenue	49,448	38,344	127,322	98,958
Advanced Packaging, Other Processing Tools, Services and Spares [Member]
Disaggregated Revenue Information [Abstract]
Revenue	$ 17,565	$ 9,321	$ 37,287	$ 12,104

ACCOUNTS RECEIVABLE (Details)

ACCOUNTS RECEIVABLE (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accounts Receivable [Abstract]
Accounts receivable	$ 84,787	$ 56,441
Less: Allowance for doubtful accounts	0	0
Total	$ 84,787	$ 56,441

INVENTORIES (Details)

INVENTORIES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Inventory [Abstract]
Raw materials	$ 65,029	$ 32,391
Work in process	29,682	23,871
Finished goods	81,898	32,377
Total inventory	176,609	88,639
Inventory reserve	1,112	1,140
First-Tools [Member]
Inventory [Abstract]
Finished goods	81,898	32,275
Contractual Obligation [Member]
Inventory [Abstract]
Finished goods	$ 58,928	$ 20,834

PROPERTY, PLANT AND EQUIPMENT_3

PROPERTY, PLANT AND EQUIPMENT, NET (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Total cost	$ 11,780		$ 11,780		$ 9,627
Less: Total accumulated depreciation	(5,120)		(5,120)		(3,745)
Construction in progress	3,345		3,345		2,310
Total property, plant and equipment, net	10,005		10,005		8,192
Depreciation expense	501	$ 195	1,407	$ 569
Manufacturing Equipment [Member]
Property, Plant and Equipment [Abstract]
Total cost	6,992		6,992		5,966
Office Equipment [Member]
Property, Plant and Equipment [Abstract]
Total cost	1,642		1,642		1,047
Transportation Equipment [Member]
Property, Plant and Equipment [Abstract]
Total cost	214		214		216
Leasehold Improvement [Member]
Property, Plant and Equipment [Abstract]
Total cost	$ 2,932		$ 2,932		$ 2,398

LAND USE RIGHT, NET (Details)

LAND USE RIGHT, NET (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Jul. 31, 2020ft²
Land use Right [Abstract]
Land use right purchase amount	$ 9,801	$ 9,801	$ 9,744
Less: Accumulated amortization	(245)	(245)	(98)
Land use right, net	9,556	9,556	9,646
Amortization	$ 49	$ 147
Remaining Amortization of Land use Right [Abstract]
2021			49
2022			196
2023			196
2024			196
2025			$ 196
Shangwei Research (Shanghai), Inc. [Member]
Land use Right [Abstract]
Right to use land lease term		50 years
Area for development and production center | ft²				1,000,000

OTHER LONG-TERM ASSETS (Details

OTHER LONG-TERM ASSETS (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Other Long-term Assets [Abstract]
Prepayment for property - Lingang	$ 40,433	$ 39,450
Prepayment for property, plant and equipment and other non-current assets	1,692	0
Prepayment for property - lease deposit	422	0
Security deposit for land use right	760	756
Others	936	290
Total other long-term assets	44,243	$ 40,496
Capitalized interest charges related to property	$ 757

SHORT-TERM BORROWINGS (Details)

SHORT-TERM BORROWINGS (Details) ₩ in Thousands, ¥ in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021CNY (¥)	Sep. 30, 2021KRW (₩)	Dec. 31, 2020USD ($)
Short-Term Borrowings [Abstract]
Short-term borrowings		$ 15,201		$ 15,201				$ 26,147
Interest expense related to short-term borrowings		176	$ 272	556	$ 611
Line of Credit Due on April 1, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[1]	0		$ 0				4,599
Maximum borrowing capacity | ¥						¥ 80,000
Annual interest rate				4.70%
Line of credit due date				Mar. 23, 2021
Line of Credit Due on June 27, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[1]	0		$ 0				1,380
Maximum borrowing capacity | ¥						80,000
Annual interest rate				4.25%
Line of credit due date				Jun. 28, 2021
Line of Credit Due on April 29, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[1]	0		$ 0				820
Maximum borrowing capacity | ¥						80,000
Annual interest rate				2.80%
Line of credit due date				Mar. 23, 2021
Line of Credit Due on June 27, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[1]	0		$ 0				2,080
Maximum borrowing capacity | ¥						80,000
Annual interest rate				2.70%
Line of credit due date				Jun. 25, 2021
Line of Credit Due on April 12, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		0		$ 0				1,533
Maximum borrowing capacity | ¥						20,000
Annual interest rate				4.65%
Line of credit due date				Apr. 12, 2021
Line of Credit Due on May 24, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		0		$ 0				1,533
Maximum borrowing capacity | ¥						20,000
Annual interest rate				3.65%
Line of credit due date				May 24, 2021
Line of Credit Due on May 27, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[2]	0		$ 0				2,575
Maximum borrowing capacity | ¥						70,000
Annual interest rate				4.68%
Line of credit due date				May 27, 2021
Line of Credit Due on June 27, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[2]	0		$ 0				1,380
Maximum borrowing capacity | ¥						70,000
Annual interest rate				4.68%
Line of credit due date				Mar. 29, 2021
Line of Credit Due on May 28, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[2]	0		$ 0				2,442
Maximum borrowing capacity | ¥						70,000
Annual interest rate				3.48%
Line of credit due date				May 28, 2021
Line of Credit Due on June 7, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[2]	0		$ 0				1,521
Maximum borrowing capacity | ¥						70,000
Annual interest rate				3.50%
Line of credit due date				Jun. 7, 2021
Line of Credit Due on June 16, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[2]	0		$ 0				1,838
Maximum borrowing capacity | ¥						70,000
Annual interest rate				3.50%
Line of credit due date				Jun. 16, 2021
Line of Credit Due on August 10, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		0		$ 0				1,380
Maximum borrowing capacity | ¥						80,000
Annual interest rate				3.85%
Line of credit due date				Aug. 10, 2021
Line of Credit Due on August 25, 2021 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		0		$ 0				3,066
Maximum borrowing capacity | ¥						80,000
Annual interest rate				3.85%
Line of credit due date				Aug. 25, 2021
Line of Credit Due on February 1, 2022 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		1,388		$ 1,388				0
Maximum borrowing capacity | ¥						80,000
Annual interest rate				3.85%
Line of credit due date				Feb. 1, 2022
Line of Credit Due on May 26, 2022 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		1,388		$ 1,388				0
Maximum borrowing capacity | ¥						80,000
Annual interest rate				3.90%
Line of credit due date				May 26, 2022
Line of Credit Due on February 2, 2022 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		1,465		$ 1,465				0
Maximum borrowing capacity | ¥						80,000
Annual interest rate				3.95%
Line of credit due date				Feb. 2, 2022
Line of Credit Due on February 2 2022 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		1,465		$ 1,465				0
Maximum borrowing capacity | ¥						80,000
Annual interest rate				3.95%
Line of credit due date				Feb. 2, 2022
Line of Credit Due on February 2, 2022 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		1,387		$ 1,387				0
Maximum borrowing capacity | ¥						80,000
Annual interest rate				3.95%
Line of credit due date				Feb. 2, 2022
Line of Credit Due on June 7, 2022 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[3]	4,618		$ 4,618				0
Maximum borrowing capacity | ¥						100,000
Annual interest rate				2.70%
Line of credit due date				Jun. 7, 2022
Line of Credit Due on June 15, 2022 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings		3,068		$ 3,068				0
Maximum borrowing capacity | ¥						¥ 40,000
Annual interest rate				3.86%
Line of credit due date				Jun. 15, 2022
Line of Credit Due on July 11, 2022 [Member]
Short-Term Borrowings [Abstract]
Short-term borrowings	[4]	$ 422		$ 422				$ 0
Maximum borrowing capacity | ₩							₩ 500,000
Annual interest rate				5.40%
Line of credit due date				Jul. 11, 2022
[1]	Guaranteed by ACM’s Chief Executive Officer
[2]	Guaranteed by ACM’s Chief Executive Officer and CleanChip
[3]	Guaranteed by CleanChip
[4]	Guaranteed by ACM Korea’s Chief Executive Officer

OTHER PAYABLE AND ACCRUED EXP_3

OTHER PAYABLE AND ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
OTHER PAYABLE AND ACCRUED EXPENSES [Abstract]
Accrued commissions	$ 10,527	$ 7,127
Accrued warranty	5,117	3,975
Accrued payroll	3,492	3,068
Accrued professional fees	40	384
Accrued machine testing fees	1,825	1,595
Others	4,949	2,656
Total	$ 25,950	$ 18,805

LEASES (Details)

LEASES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Components of lease expense [Abstract]
Operating lease cost	$ 632	$ 384	$ 1,807	$ 1,139
Short-term lease cost	105	73	258	170
Lease cost	737	457	2,065	1,309
Cash paid for amounts included in the measurement of lease liabilities [Abstract]
Operating cash outflow from operating leases	737	$ 457	2,065	$ 1,309
Maturities of lease liabilities [Abstract]
2021	631		631
2022	2,292		2,292
2023	1,020		1,020
2024	914		914
2025	19		19
Total lease payments	4,876		4,876
Less: Interest	(277)		(277)
Present value of lease liabilities	$ 4,599		$ 4,599
Weighted average remaining lease terms and discount rates [Abstract]
Weighted average remaining lease term	1 year 6 months		1 year 6 months		2 years 1 month 9 days
Weighted average discount rate	4.58%		4.58%		5.14%

LONG-TERM BORROWINGS (Details)

LONG-TERM BORROWINGS (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2021USD ($)Intallment	Dec. 31, 2020USD ($)
Long-Term Borrowings [Abstract]
Long-term debt	$ 25,431	$ 25,431
Less: Current portion	(2,351)	(2,351)	$ (1,591)
Long-term Borrowings	23,080	23,080	17,979
Principal Payments of Long-Term Loan [Abstract]
2021	484	484
2022	2,370	2,370
2023	2,450	2,450
2024	7,313	7,313
2025 and onwards	12,814	12,814
Long-term debt	25,431	25,431
Interest expense related to long-term borrowings incurred	232	776
Interest expense charged to long-term borrowings	15	18
Capitalized interest charged as other long-term assets	217	758
China Merchants Bank [Member]
Long-Term Borrowings [Abstract]
Long-term debt	18,492	$ 18,492	19,570
Number of installments for loan repayable | Intallment		120
Last installment due date		Nov. 30, 2030
Annual interest rate		4.65%
Principal Payments of Long-Term Loan [Abstract]
Long-term debt	18,492	$ 18,492	19,570
Bank of China [Member]
Long-Term Borrowings [Abstract]
Long-term debt	6,939	6,939	0
Principal Payments of Long-Term Loan [Abstract]
Long-term debt	$ 6,939	$ 6,939	$ 0
Bank of China [Member] | Loan 1 [Member]
Long-Term Borrowings [Abstract]
Number of installments for loan repayable | Intallment		6
Last installment due date		Jun. 30, 2024
Annual interest rate		2.60%
Bank of China [Member] | Loan 2 [Member]
Long-Term Borrowings [Abstract]
Number of installments for loan repayable | Intallment		6
Last installment due date		Sep. 30, 2024
Annual interest rate		2.60%

OTHER LONG-TERM LIABILITIES (De

OTHER LONG-TERM LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Other Long-term Liabilities [Abstract]
Other long-term liabilities	$ 5,303	$ 8,034
Subsidies to Stress Free Polishing Project, Commenced in 2008 and 2017 [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	949	1,266
Subsidies to Electro Copper Plating Project, Commenced in 2014 [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	901	2,156
Subsidies to Polytetrafluoroethylene, Commenced in 2018 [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	0	130
Subsidies to Tahoe-Single Bench Clean, Commenced in 2020 [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	185	1,544
Subsidies to Backside Clean-YMTC National Project, Commenced in 2020 [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	2,779	2,591
Other [Member]
Other Long-term Liabilities [Abstract]
Other long-term liabilities	$ 489	$ 347

LONG-TERM INVESTMENT (Details)

LONG-TERM INVESTMENT (Details) $ / shares in Units, ¥ in Thousands, $ in Thousands	Sep. 05, 2019shares	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2019CNY (¥)	Jun. 27, 2019USD ($)	Sep. 11, 2017USD ($)$ / sharesshares
Classification of Investments [Abstract]
Total		$ 7,408		$ 7,408		$ 6,340
Equity income in net income of affiliates		421	$ 182	1,036	$ 539
Ninebell [Member]
Investments [Abstract]
Percentage of ordinary shares issued										20.00%
Purchase price										$ 1,200
Classification of Investments [Abstract]
Total		2,713		2,713		1,666
Ninebell [Member] | Class A Common Stock [Member]
Investments [Abstract]
Purchase price										$ 1,000
Shares issued (in shares) | shares										133,334
Share price (in dollars per share) | $ / shares										$ 7.50
Shengyi [Member]
Investments [Abstract]
Percentage of ordinary shares issued									15.00%
Investment - equity method									$ 109
Number of investors with agreements entered | shares	6
Classification of Investments [Abstract]
Total		186		186		134
Hefei Shixi [Member]
Investments [Abstract]
Investment in partnership							$ 4,200	¥ 30,000
Ownership percentage in partnership							10.00%	10.00%
Classification of Investments [Abstract]
Total		$ 4,509		$ 4,509		$ 4,540

FINANCIAL LIABILITY CARRIED A_3

FINANCIAL LIABILITY CARRIED AT FAIR VALUE (Details) $ / shares in Units, ¥ in Thousands, $ in Thousands

Jun. 09, 2021USD ($)shares

Jul. 29, 2020USD ($)$ / sharesshares

Apr. 30, 2020USD ($)Agreementshares

Aug. 31, 2019USD ($)$ / sharesshares

Mar. 31, 2018USD ($)shares

Mar. 31, 2017USD ($)$ / sharesshares

Sep. 30, 2021USD ($)

Sep. 30, 2020USD ($)

Sep. 30, 2021USD ($)

Sep. 30, 2020USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2016CNY (¥)

Related Party Transaction [Abstract]

Change in fair value of financial liability

$ 0

$ 6,533

$ 0

$ 11,964

Issuance of warrant for settlement of financial liability

$ 0

$ 19,859

2020 Warrants [Member]

Related Party Transaction [Abstract]

Financial liability carried at fair value

$ 21,679

Change in fair value of financial liability

$ 11,964

Fair value warrant amount

21,679

Fair Value of Options Granted [Abstract]

Fair value of common share (in dollars per share) | $ / shares

[1]

$ 89.28

Expected term

[2]

3 years 5 months 1 day

Volatility

[3]

47.42%

Risk-free interest rate

[4]

0.15%

Expected dividend

[5]

0.00%

Common Class A [Member] | 2020 Warrants [Member]

Related Party Transaction [Abstract]

Shares issued (in shares) | shares

242,681

Fair Value of Options Granted [Abstract]

Fair value of common share (in dollars per share) | $ / shares

$ 7.50

ACM Shanghai [Member]

Related Party Transaction [Abstract]

Repayments of notes

$ 1,161

Number of agreement | Agreement

2

ACM Shanghai [Member] | Senior Secured Promissory Note [Member]

Related Party Transaction [Abstract]

Receivables

$ 1,820

ACM Shanghai [Member] | Intercompany Note [Member]

Related Party Transaction [Abstract]

Promissory note principal amount

$ 2,981

Interest rate on promissory note

3.01%

Promissory note maturity date

Aug. 17, 2023

Fair value warrant amount

$ 1,820

SMC [Member]

Related Party Transaction [Abstract]

Payment for investment

$ 2,981

¥ 20,123,500

Shares issued value

$ 1,820

Investment repayment period

60 days

Number of shares repurchased/surrender in exchange (in shares) | shares

242,681

154,821

Repayments of notes

$ 882

Investment due amount

$ 1,820

Consideration price in fair value

$ 9,715

Issuance of warrant for settlement of financial liability

$ 19,859

Fair Value of Options Granted [Abstract]

Fair value of common share (in dollars per share) | $ / shares

$ 13.195

SMC [Member] | Senior Secured Promissory Note [Member]

Related Party Transaction [Abstract]

Promissory note principal amount

$ 2,981

Interest rate on promissory note

3.01%

Promissory note maturity date

Aug. 17, 2023

SMC [Member] | Common Class A [Member]

Related Party Transaction [Abstract]

Shares issued (in shares) | shares

242,681

397,502

Shares issued value

$ 2,981

Fair Value of Options Granted [Abstract]

Fair value of common share (in dollars per share) | $ / shares

$ 13.195

$ 7.50

SMC [Member] | Common Class A [Member] | Senior Secured Promissory Note [Member]

Related Party Transaction [Abstract]

Exercise of common stock warrant issued (in shares) | shares

397,502

SMC [Member] | ACM Shanghai [Member]

Related Party Transaction [Abstract]

Repayment of investment in cash

$ 1,820

$ 1,161

[1]

Fair value of Class A common stock was the closing market price of the Class A common stock on July 29, 2020.

[2]

Expected term of share options was based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110.

[3]

Volatility was calculated based on the historical volatility of the stock of companies comparable to ACM in the period equal to the expected term of each grant.

[4]

Risk-free interest rate was based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant.

[5]

Expected dividend was assumed to be 0%, as ACM had no history or expectation of paying a dividend on its common stock.

TRADING SECURITIES (Details)

TRADING SECURITIES (Details) $ in Thousands, ¥ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Jun. 18, 2020CNY (¥)	Jun. 18, 2020USD ($)
Trading securities listed in Shanghai Stock Exchange [Abstract]
Cost	$ 15,108		$ 15,108		$ 15,020
Market value	30,219		30,219		$ 28,239
Unrealized gain (loss) on trading securities	$ (919)	$ 8,970	$ 1,817	$ 8,970
Qingdao LP [Member]
Investments [Abstract]
Total capital fund of limited partnership						¥ 2,224	$ 315,000
Investment in partnership						¥ 100	$ 14,200
Ownership percentage in partnership						4.30%	4.30%
SMIC [Member] | Minimum [Member]
Investments [Abstract]
Ownership percentage in partnership	30.00%		30.00%

RELATED PARTY BALANCES AND TR_3

RELATED PARTY BALANCES AND TRANSACTIONS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transaction [Abstract]
Accounts payable	$ 8,260		$ 8,260		$ 4,093
Purchase of materials	8,563	$ 4,628	23,586	$ 10,665
Service fee charged by	144	36	403	226
Ninebell Co., Ltd [Member]
Related Party Transaction [Abstract]
Prepaid expenses	2,192		2,192		1,607
Accounts payable	6,340		6,340		2,898
Purchase of materials	7,455	4,029	21,833	9,552
Service fee charged by	0	22	0	22
Shengyi Semiconductor Technology Co., Ltd [Member]
Related Party Transaction [Abstract]
Accounts payable	1,920		1,920		$ 1,195
Purchase of materials	1,108	599	1,753	1,113
Service fee charged by	$ 144	$ 14	$ 403	$ 204

COMMON STOCK (Details)

COMMON STOCK (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021Vote$ / sharesshares	Sep. 30, 2020shares	Sep. 30, 2021Vote$ / sharesshares	Sep. 30, 2020shares	Dec. 31, 2020$ / sharesshares
Class of Stock [Abstract]
Number of shares cancelled (in shares)				242,681
Common Class A [Member]
Class of Stock [Abstract]
Common stock, shares authorized (in shares)	150,000,000		150,000,000		50,000,000
Additional shares reserved for issuance as dividends (in shares)	60,000,000		60,000,000
Common stock, additional shares authorized (in shares)	100,000,000		100,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001		$ 0.0001		$ 0.0001
Number of votes for each share entitled | Vote	1		1
Common stock, shares issued (in shares)	17,798,740		17,798,740		16,896,693
Common stock, shares outstanding (in shares)	17,798,740		17,798,740		16,896,693
Common Class B [Member]
Class of Stock [Abstract]
Common stock, shares authorized (in shares)	5,307,816		5,307,816		2,409,738
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001		$ 0.0001		$ 0.0001
Number of votes for each share entitled | Vote	20		20
Convertible shares in to Class A common stock (in shares)			1
Common stock, shares issued (in shares)	1,707,605		1,707,605		1,802,606
Common stock, shares outstanding (in shares)	1,707,605		1,707,605		1,802,606
Common Stock [Member] | Common Class A [Member]
Class of Stock [Abstract]
Stock issued upon exercise of stock options (in shares)	130,331	407,043	564,365	592,946
Conversion of class B common stock to Class A common stock (in shares)			95,001	60,002
Exercise of common stock warrant issued (in shares)			242,681	64,717
Number of shares repurchased/surrender in exchange (in shares)				242,681
Common Stock [Member] | Common Class B [Member]
Class of Stock [Abstract]
Stock issued upon exercise of stock options (in shares)	0	0	0	0
Conversion of class B common stock to Class A common stock (in shares)			(95,001)	(60,002)
Exercise of common stock warrant issued (in shares)			0	0

REDEEMABLE NON-CONTROLLING IN_3

REDEEMABLE NON-CONTROLLING INTERESTS (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
REDEEMABLE NON-CONTROLLING INTERESTS [Abstract]
Redeemable non-controlling interest	$ 0
Change in Redeemable Non-controlling Interests [Abstract]
Balance	60,162
Net income attributable to redeemable non-controlling interests	643
Effect of foreign currency translation gain attributable to redeemable non-controlling interests	(847)
Reclassification of redeemable non-controlling interest	(59,958)
Balance	$ 0

STOCK-BASED COMPENSATION, Stock

STOCK-BASED COMPENSATION, Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-based Compensation Expense [Abstract]
Stock-based compensation expense	$ 1,278	$ 2,779	$ 3,823	$ 4,323
Employee Stock Purchase Plan [Member]
Stock-based Compensation Expense [Abstract]
Stock-based compensation expense	1,179	2,651	3,481	3,717
Employee Stock Purchase Plan [Member] | ACM Shanghai [Member]
Stock-based Compensation Expense [Abstract]
Stock-based compensation expense	87	84	260	250
Non-Employee Stock Purchase Plan [Member]
Stock-based Compensation Expense [Abstract]
Stock-based compensation expense	12	44	82	356
Cost of Revenue [Member]
Stock-based Compensation Expense [Abstract]
Stock-based compensation expense	108	44	289	132
Sales and Marketing Expense [Member]
Stock-based Compensation Expense [Abstract]
Stock-based compensation expense	417	237	1,400	495
Research and Development Expense [Member]
Stock-based Compensation Expense [Abstract]
Stock-based compensation expense	293	193	801	568
General and Administrative Expense [Member]
Stock-based Compensation Expense [Abstract]
Stock-based compensation expense	$ 460	$ 2,305	$ 1,333	$ 3,128

STOCK-BASED COMPENSATION, Share

STOCK-BASED COMPENSATION, Share Option Activities (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Employee Share Option [Member]
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares) | shares	3,191,411
Granted (in shares) | shares	138,400
Exercised (in shares) | shares	(443,683)
Forfeited/cancelled (in shares) | shares	(33,404)
Outstanding, end of period (in shares) | shares	2,852,724	3,191,411
Vested and exercisable (in shares) | shares	1,844,193
Weighted Average Grant Date Fair Value [Abstract]
Outstanding at beginning of period (in dollars per share)	$ 5.13
Granted (in dollars per share)	48.18
Exercised (in dollars per share)	2.39
Forfeited/cancelled (in dollars per share)	32.66
Outstanding at end of period (in dollars per share)	7.32	$ 5.13
Weighted Average Exercise Price [Abstract]
Outstanding, beginning of period (in dollars per share)	12.73
Granted (in dollars per share)	106.15
Exercised (in dollars per share)	6.15
Forfeited/cancelled (in dollars per share)	73.94
Outstanding, end of period (in dollars per share)	$ 17.57	$ 12.73
Weighed Average Remaining Contractual Term [Abstract]
Outstanding weighed average remaining contractual term	6 years 9 months 10 days	7 years 1 month 17 days
Unrecognized employee stock-based compensation expense | $	$ 10,677	$ 8,733
Weighted-average period over which unrecognized compensation is expected to be recognized	1 year 9 months 25 days	1 year 10 months 20 days
Employee Share Option [Member] | ACM Shanghai [Member]
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares) | shares	5,423,654
Granted (in shares) | shares	0
Exercised (in shares) | shares	0
Expired (in shares) | shares	0
Forfeited/cancelled (in shares) | shares	(46,154)
Outstanding, end of period (in shares) | shares	5,377,500	5,423,654
Vested and exercisable (in shares) | shares	0
Weighted Average Grant Date Fair Value [Abstract]
Outstanding at beginning of period (in dollars per share)	$ 0.23
Granted (in dollars per share)	0
Exercised (in dollars per share)	0
Expired (in dollars per share)	0
Forfeited/cancelled (in dollars per share)	0.24
Outstanding at end of period (in dollars per share)	0.24	$ 0.23
Weighted Average Exercise Price [Abstract]
Outstanding, beginning of period (in dollars per share)	1.89
Granted (in dollars per share)	0
Exercised (in dollars per share)	0
Expired (in dollars per share)	0
Forfeited/cancelled (in dollars per share)	2.01
Outstanding, end of period (in dollars per share)	$ 2.01	$ 1.89
Weighed Average Remaining Contractual Term [Abstract]
Outstanding weighed average remaining contractual term	2 years 9 months 3 days	3 years 6 months
Non-Employee Stock Option [Member]
Number of Option Share [Roll Forward]
Outstanding, beginning of period (in shares) | shares	836,038
Granted (in shares) | shares	0
Exercised (in shares) | shares	(120,682)
Expired (in shares) | shares	0
Forfeited/cancelled (in shares) | shares	(250)
Outstanding, end of period (in shares) | shares	715,106	836,038
Vested and exercisable (in shares) | shares	702,606
Weighted Average Grant Date Fair Value [Abstract]
Outstanding at beginning of period (in dollars per share)	$ 1.02
Granted (in dollars per share)	0
Exercised (in dollars per share)	1.23
Expired (in dollars per share)	0
Forfeited/cancelled (in dollars per share)	0.30
Outstanding at end of period (in dollars per share)	0.99	$ 1.02
Weighted Average Exercise Price [Abstract]
Outstanding, beginning of period (in dollars per share)	3.07
Granted (in dollars per share)	0
Exercised (in dollars per share)	4.29
Expired (in dollars per share)	0
Forfeited/cancelled (in dollars per share)	0.75
Outstanding, end of period (in dollars per share)	$ 2.86	$ 3.07
Weighed Average Remaining Contractual Term [Abstract]
Outstanding weighed average remaining contractual term	4 years 1 month 24 days	4 years 11 months 1 day
Unrecognized employee stock-based compensation expense | $	$ 113	$ 195
Weighted-average period over which unrecognized compensation is expected to be recognized	25 days	1 month 2 days
Non-Employee Stock Option [Member] | ACM Shanghai [Member]
Weighed Average Remaining Contractual Term [Abstract]
Unrecognized employee stock-based compensation expense | $	$ 605	$ 822
Weighted-average period over which unrecognized compensation is expected to be recognized	1 year 9 months	2 years 6 months

STOCK-BASED COMPENSATION, Assum

STOCK-BASED COMPENSATION, Assumptions Used to Determine Fair Value of Share Options Granted (Details) - Employee Share Option [Member] - Service Period Based [Member]	9 Months Ended
	Sep. 30, 2021$ / shares
Fair Value of Options Granted [Abstract]
Expected dividend	0.00%	[1]
Minimum [Member]
Fair Value of Options Granted [Abstract]
Fair value of common share (in dollars per share)	$ 82.75	[2]
Expected term in years	5 years 6 months	[3]
Volatility	48.53%	[4]
Risk-free interest rate	1.00%	[5]
Maximum [Member]
Fair Value of Options Granted [Abstract]
Fair value of common share (in dollars per share)	$ 111.98	[2]
Expected term in years	6 years 3 months	[3]
Volatility	49.47%	[4]
Risk-free interest rate	1.12%	[5]
[1]	Expected dividend is assumed to be 0% as ACM has no history or expectation of paying a dividend on its common stock.
[2]	Equal to closing value on the grant date.
[3]	Expected term of share options is based on the average of the vesting period and the contractual term for each grant according to Staff Accounting Bulletin 110.
[4]	Volatility is calculated based on the historical volatility of ACM’s comparable companies in the period equal to the expected term of each grant.
[5]	Risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant.

INCOME TAXES (Details)

INCOME TAXES (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)Subsidiary	Sep. 30, 2020USD ($)
Income Taxes [Abstract]
Statutory U.S federal income tax rate			21.00%
Unrecognized tax benefits	$ 570		$ 570
Unrecognized tax benefits that would impact effective tax rate	422		422
Interest or penalties			0
Income Tax Benefit (Expense) [Abstract]
Total income tax benefit (expense)	$ 266	$ 1,747	$ 3,021	$ (416)
ACM Research (Shanghai), Inc. [Member]
Income Taxes [Abstract]
Foreign corporate tax rate			15.00%
PRC [Member]
Income Taxes [Abstract]
Number of subsidiaries | Subsidiary			3
Foreign corporate tax rate			25.00%
Effective period of preferential income tax rate			3 years
PRC [Member] | Minimum [Member]
Income Taxes [Abstract]
Foreign corporate tax rate			12.50%
PRC [Member] | Maximum [Member]
Income Taxes [Abstract]
Foreign corporate tax rate			25.00%
PRC [Member] | ACM Research (Shanghai), Inc. [Member]
Income Taxes [Abstract]
Foreign corporate tax rate			12.50%
PRC [Member] | ACM Research (Wuxi), Inc. [Member]
Income Taxes [Abstract]
Foreign corporate tax rate			25.00%
PRC [Member] | Shengwei Research (Shanghai), Inc. [Member]
Income Taxes [Abstract]
Foreign corporate tax rate			16.50%

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands, ¥ in Millions	9 Months Ended
	Sep. 30, 2021USD ($)LegalProceeding	Sep. 30, 2021CNY (¥)	Dec. 21, 2020ExecutiveOfficers
COMMITMENTS AND CONTINGENCIES [Abstract]
Commitments	$ 2,663
Required liquidate damage value	$ 63,400	¥ 450
Land use rights period	6 years	6 years
Annual total taxes	$ 22,000	¥ 157.6
Investments	$ 10,977
Number of outstanding legal proceedings | LegalProceeding	1
Number of executive officers against lawsuit filed | ExecutiveOfficers			3

SUBSEQUENT EVENT (Details)

SUBSEQUENT EVENT (Details) - Nov. 04, 2021 - Subsequent Event [Member] - ACM Shanghai [Member] - IPO [Member] ¥ / shares in Units, $ in Thousands, ¥ in Millions	CNY (¥)¥ / sharesshares	USD ($)shares
Subsequent Event [Line Items]
Offering of shares (in shares)	43,355,753	43,355,753
Percentage amount of shares offered from shares outstanding	10.00%
Common stock, shares outstanding (in shares)	433,557,100
Share price (in RMB per share) | ¥ / shares	¥ 85
Gross proceeds of stock issuance	¥ 3,685	$ 575,000
Percentage of shares owned by Company after stock issuance	82.50%	82.50%