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                                                                   Exhibit 10.64



                             SUPPLEMENTAL AGREEMENT


                                  in respect of


                     LOAN AGREEMENT DATED SEPTEMBER 30, 1998


                                     between


                             LAM RESEARCH CO., LTD.
                                   as Borrower


                THE BANKS AND FINANCIAL INSTITUTIONS NAMED HEREIN
                                   as Lenders


                        ABN AMRO BANK N.V., TOKYO BRANCH
                                    as Agent


                                       and


                        ABN AMRO BANK N.V., TOKYO BRANCH
                                as Initial Lender



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THIS SUPPLEMENTAL AGREEMENT is entered into on the 25th of December, 1998

BETWEEN:

(1)     LAM RESEARCH CO., LTD., a Japanese corporation having its registered
        office at 1-1-10, Oyama, Sagamihara-shi, Kanagawa Prefecture, Japan as
        borrower (the "BORROWER");

(2)     THE BANKS AND FINANCIAL INSTITUTIONS NAMED IN THE SIGNATURE PAGE HEREOF
        as lenders (collectively, the "LENDERS" and each a "LENDER");

(3)     ABN AMRO BANK N.V. acting through its TOKYO BRANCH, a branch licensed in
        Japan and having its registered office at Shiroyama JT Mori Building,
        4-3-1, Toranomon, Minato-ku, Tokyo 105-6013, Japan, as agent of the
        Lenders (in such capacity, the "AGENT"); and

(4)     ABN AMRO BANK N.V. acting through its TOKYO BRANCH, a branch licensed in
        Japan and having its registered office at Shiroyama JT Mori Building,
        4-3-1, Toranomon, Minato-ku, Tokyo 105-6013, Japan, as the initial
        lender (the "INITIAL LENDER").


WHEREAS:

(A)     The Borrower, the Initial Lender and the Agent have entered into a Loan
        Agreement dated September 30, 1998 (the "ORIGINAL AGREEMENT"), pursuant
        to which the Initial Lender has provided a loan to the Borrower in the
        amount of (Y)1,700,000,000; and

(B)     The parties hereto wish to amend certain terms of the Original
        Agreement, to the extent provided below.

IT IS HEREBY AGREED as follows:-

1.      GENERAL

        (1) Terms defined in the Original Agreement (if applicable, as amended
by this Agreement) shall, when used in this Agreement (including in the
Recital), have the same meanings herein as therein, unless otherwise
specifically provided herein.

        (2) Except insofar as amended by this Agreement, the Original Agreement
shall continue in full force and effect and shall be read and construed as one
with this Agreement. Upon this Agreement taking effect, references in the
Original Agreement to "this Agreement", "herein", "hereunder" and other similar
expressions shall be deemed to be references to the Original Agreement to the
extent amended and restated by this Agreement.

        (3) This Agreement shall be governed by and construed in accordance with
the laws of Japan and the provisions of Clause 18.2 (Jurisdiction) of the
Original Agreement shall be deemed to apply to this Agreement as though they
were set out in full herein.



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                                      -2-


        (4) The headings are for convenience of reference only and shall not
affect the construction hereof.

        (5) This Agreement may be signed in any number of counterparts. Any
single counterpart or a set of counterparts signed, in either case, by all the
parties hereto shall constitute a full and original agreement for all purposes.

2.      AMENDMENT TO ORIGINAL AGREEMENT

        Subject to Clause 4 hereof, effective as of December 25, 1998 (the
"EFFECTIVE DATE"), the Original Agreement shall be amended as follows:

        (1)     Clause 5.3 of the Original Agreement shall be amended in its
entirety to read as follows:

        (a)    The Margin shall be (i) in respect of the period from and
               including the Drawdown Date to and including the date immediately
               preceding December 25, 1998 (the "EFFECTIVE DATE"), 0.90 percent
               per annum and (ii) in respect of the period from and including
               the Effective Date to and including December 26, 1999, 1.50
               percent per annum.

        (b)    On or after December 27, 1999, the Margin shall be, in respect of
               any Margin Period:

               (i)    if the Guarantor does not have net profits of greater than
                      US$1, as determined in accordance with generally accepted
                      accounting principles and practices in the United States
                      of America as consistently applied, during both the fiscal
                      quarter ending on September 26, 1999 and the fiscal
                      quarter ending on December 26, 1999, 1.50 percent per
                      annum;

               (ii)   if the Guarantor has net profits of greater than US$1, as
                      determined in accordance with generally accepted
                      accounting principles and practices in the United States
                      of America as consistently applied, during both the fiscal
                      quarter ending on September 26, 1999 and the fiscal
                      quarter ending on December 26, 1999 and the Senior
                      Indebtedness Ratio of the Guarantor as set forth in the
                      quarterly financial statements and information of the
                      Guarantor for the fiscal quarter ending immediately
                      preceding the first day of the relevant Margin Period is
                      less than 0.10, 0.75 percent per annum;

               (iii)  if the Guarantor has net profits of greater than US$1, as
                      determined in accordance with generally accepted
                      accounting principles and practices in the United States
                      of America as consistently applied, during both the fiscal
                      quarter ending on September 26, 1999 and the fiscal
                      quarter ending on December 26, 1999 and the Senior
                      Indebtedness Ratio of the Guarantor as set forth in the
                      quarterly financial statements and information of the
                      Guarantor for the fiscal quarter ending immediately
                      preceding the first day of the relevant Margin Period is
                      greater than or equal to 0.10 but less than 0.15, 1.00
                      percent per annum; or




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                                      -3-



               (iv)   if the Guarantor has net profits of greater than US$1, as
                      determined in accordance with generally accepted
                      accounting principles and practices in the United States
                      of America as consistently applied, during both the fiscal
                      quarter ending on September 26, 1999 and the fiscal
                      quarter ending on December 26, 1999 and the Senior
                      Indebtedness Ratio of the Guarantor as set forth in the
                      quarterly financial statements and information of the
                      Guarantor for the fiscal quarter ending immediately
                      preceding the first day of the relevant Margin Period is
                      greater than or equal to 0.15 but less than or equal to
                      0.25, 1.25 percent per annum.

        (c)    Notwithstanding the provisions of Clauses 5.3(a) and 5.3(b), if
               and so long as cash collateral is deposited by the Borrower in
               accordance with Clause 10.1(h), the Margin applicable to the
               portion of the Loan that corresponds to the amount of such cash
               collateral shall be 0.30 percent per annum.

        (d)    Notwithstanding the provisions of Clause 5.3(b), if the Guarantor
               fails to deliver to the Agent the financial statements and
               information required under clause (i) and (ii) of Subparagraphs
               4(a) of the Guaranty within the time periods set forth therein,
               the Margin shall be, in respect of any period from and including
               the fifteenth day following the date of such failure to and
               including the fifteenth day following receipt by the Agent of
               such financial statements and information (at which time Clause
               5.3(b) or 5.3(c) above, as applicable, shall apply), 1.50 percent
               per annum.

        (e)    Except where item (i) of Clause 5.3(b) above shall be applicable,
               the Borrower shall notify the Agent of the Senior Indebtedness
               Ratio of the Guarantor applicable to each Margin Period and shall
               submit Margin Certificates (duly completed and signed by a duly
               authorized officer of the Guarantor), and supporting evidence in
               respect thereof on or before the first day of such Margin Period.

        (2)     The following Clause 10.1(h) shall be inserted immediately after
Clause 10.1(g) of the Original Agreement:

               (h)    No later than March 1, 1999, the Borrower shall deposit
                      cash collateral in the amount of(Y)850,000,000 with ABN
                      AMRO Bank N.V., acting through its Tokyo Branch (the
                      "INITIAL LENDER") at the Borrower's account (current
                      account, account No.: [ ]) at the Initial Lender (the
                      "COLLATERAL ACCOUNT"). To secure the Borrower's
                      obligations to the Initial Lender under this Agreement, as
                      of the date the Borrower deposits such cash collateral in
                      the Collateral Account, the Borrower hereby creates a
                      pledge (shichiken) in favor of the Initial Lender over all
                      its rights and interests in and to the Collateral Account
                      and any moneys and balances from time to time deposited
                      therein or standing to the credit thereto or any proceeds
                      thereof and submits a passbook or deposit certificate for
                      the Collateral Account to the Initial Lender. The Borrower
                      shall also take such necessary steps as the Initial Lender
                      reasonably requires


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                                      -4-


                      in order to satisfy the Initial Lender that such cash
                      collateral is duly pledged or otherwise constitute
                      security to secure the Loan (in part) and is duly
                      perfected. Such cash collateral shall be held by the
                      Initial Lender and may (upon the occurrence of an Event of
                      Default) be applied by the Initial Lender as security
                      against the Borrower's obligations to the Initial Lender
                      under this Agreement or through the exercise by the
                      Initial Lender against such cash collateral of its set-off
                      rights in accordance with Clause 14.1 (it being understood
                      that such cash collateral shall be deposited solely for
                      the benefit of the Initial Lender and Clause 14.2 shall
                      not apply to the application of such cash collateral to
                      discharge the Borrower's obligations to the Initial Lender
                      under this Agreement). The Borrower hereby consents to the
                      Initial Lender's immediate enforcement of such rights and
                      interests as pledgee without any notice or proof and the
                      Initial Lender shall be immediately entitled to apply any
                      funds held at the Collateral Account to satisfy the
                      Borrower's obligations to the Initial Lender under this
                      Agreement. If the Initial Lender has transferred a portion
                      (corresponding to(Y)850,000,000) of its rights, benefits
                      and/or obligations under this Agreement to another person
                      in accordance with Clause 15.4, the Borrower may withdraw
                      the above-mentioned cash collateral.

3.      REPRESENTATIONS AND WARRANTIES

        As of the Effective Date (or, with respect to the obligations of the
Borrower set forth in Clause 10.1(h), upon obtaining additional internal and
external authorizations, consents and/or approvals which shall occur no later
than March 1, 1999) the Borrower represents and warrants to the Agent and the
Lenders as follows:

        (1) it has power to enter into this Agreement and perform its
obligations hereunder and has taken all necessary action required to authorize
the execution and delivery of this Agreement, and the performance of the
Original Agreement as amended by this Agreement, upon the terms and conditions
of the Original Agreement as amended by this Agreement;

        (2) all necessary consents, approvals and authorizations required in
connection with the execution, delivery, performance, validity or enforceability
of this Agreement have been obtained and made and are in full force and effect
and each of this Agreement and the Original Agreement as amended by this
Agreement constitutes a legal, valid and binding obligation of the Borrower
enforceable in accordance with its terms;

        (3) the execution, delivery and performance of this Agreement and the
performance of the Original Agreement as amended by this Agreement will not
violate, result in a breach of, or constitute a default under, any provision of
any indenture, contract or other undertaking to which the Borrower is a party or
by which it or its property is bound or of any law or any regulation or, of any
order, writ, or decree applicable to it; and



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                                       -5-


        (4) no event has occurred and no condition exists which, with the giving
of notice or lapse of time or the satisfaction of any other condition, would
constitute an Event of Default under the Original Agreement as amended by this
Agreement.

4.      CONDITIONS PRECEDENT TO THE EFFECTIVENESS OF THIS AGREEMENT

        (1) The provisions of Clause 2 hereof shall not come into effect until
the Agent has received (i) a First Amendment to Guaranty in form and substance
satisfactory to Agent duly executed by Guarantor and (ii) a confirmation letter
from the Guarantor substantially in the form of Annex A attached hereto.

        (2) The effectiveness of Clause 2 hereof is subject to the further
condition precedent that as of the Effective Date the representations and
warranties made by the Borrower in Clause 3 hereof are true and accurate as if
the same had been made on such date.

5.      FEES AND EXPENSES

        The Borrower shall reimburse the Agent and the Lenders for all
reasonable expenses incurred by it in connection with the negotiation,
preparation and execution of this Agreement (including all legal fees and
expenses and any stamp and other duties and taxes to which this Agreement is
subject).

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed
on the day and year first before written.


THE BORROWER

LAM RESEARCH CO., LTD.



By:
   --------------------------------
   Name:
   Title:



THE AGENT AND (INITIAL) LENDER

ABN AMRO BANK N.V., TOKYO BRANCH



By:
   --------------------------------
   Name:
   Title:



By:
   --------------------------------



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                                     ANNEX A

                    [LETTERHEAD OF LAM RESEARCH CORPORATION]


                                                          Date: December 25,1998

ABN AMRO Bank N.V.
Tokyo Branch
as Agent
to the Loan Agreement referred to below
Shiroyama JT Mori Building
4-3-1, Toranomon,
Minato-ku, Tokyo 105-6013
Japan

Dear Sirs:

                               Re: Loan Agreement

               We refer to a Loan Agreement dated September 30, 1998 (the
"ORIGINAL AGREEMENT") between Lam Research Co., Ltd. ("LAM JAPAN") as Borrower,
the banks and financial institutions named therein as Lenders, and ABN AMRO Bank
N.V., Tokyo Branch as Agent and a Supplemental Agreement dated December 25, 1998
(the "SUPPLEMENTAL AGREEMENT") between Lam Japan as Borrower, the banks and
financial institutions named therein as Lenders, and ABN AMRO Bank N.V., Tokyo
Branch as Agent and Initial Lender. Terms defined in the Original Agreement as
amended by the Supplemental Agreement shall have the same meanings herein,
unless otherwise defined herein.

               We give consent to the amendments of the Original Agreement by
the Supplemental Agreement and confirm that our obligations and liabilities
under the Guaranty dated as of September 30, 1998 executed by us in connection
with the Original Agreement will continue and remain in full force and effect
with respect to the Original Agreement as amended, except to the extent amended
pursuant to that certain First Amendment to Guaranty dated as of the date
hereof.



                                    Very truly yours,

                                    LAM RESEARCH CORPORATION


                                    By:
                                       ----------------------------------------
                                       Name:
                                       Title: