Exhibit 10. 09

                 AMENDED RETENTION AND NON-COMPETITION AGREEMENT

This Amended Retention and Non-Competition  Agreement (the "Amended  Agreement")
is entered  into by and  between  KLA-Tencor  Corporation  (the  "Company")  and
Kenneth  Levy  ("Executive")  effective  as of April 29,  1998  (the  "Effective
Date").

Recitals:

A. The Company  desires to continue to retain the  services of  Executive as set
forth in this Amended  Retention  and  Non-Competition  Agreement  and Executive
desires  to  continue  to provide  services  to the  Company  upon the terms and
conditions set forth herein.

B. The Company  desires to ensure that  Executive  does not compete  with and is
available to continue to provide services to the Company as set forth herein.

Agreement:
In consideration of the covenants and agreements  contained herein,  the parties
agree as follows:

1.  Effectiveness  of Amended  Agreement.This  Amended  Agreement  shall  become
effective upon the Effective Date and amends that Retention and  Non-Competition
Agreement  dated  April  30,  1997  contemplated  by the  Agreement  and Plan of
Reorganization   (the  "Merger  Agreement")  by  and  among  Tencor  Instruments
("Tencor"), Tiger Acquisition Corp. and KLA Instruments Corporation ("KLA"). The
Company and Executive  agree that this Amended  Agreement shall govern the terms
and  conditions  of  Executive's  provision  of services to the Company from and
after the Effective Date.

2. Term.  This Amended  Agreement shall commence on the Effective Date and shall
end on the date that all obligations hereunder have been fully discharged.

3. Duties.

a. Responsibilities. From and after the Effective Date until the commencement of
any  Part-Time  Employment  Term  (as  defined  in  Section  7 of  this  Amended
Agreement) (the  "Full-Time  Employment  Period"),  the Company shall employ the
Executive with such duties and  responsibilities as determined from time to time
by the Board of Directors  (the "Board") of the Company.  It is  understood  and
agreed  that  Executive  will be  considered  an employee of the Company for tax
withholding  purposes for the duration of both the Full-Time  Employment  Period
and the Part-Time  Employment Term.  Executive  acknowledges that as a part-time
Employee he shall not have the power to bind the Company.


b. Board  Membership.  If  Executive  is serving as a member of the Board on the
date of termination of the Full-Time  Employment  Period, he shall tender to the
Board his resignation  from the Board effective as of such date. The Board shall
not be obligated to accept such resignation.

4. Obligations. Executive agrees, during the Full-Time Employment Period, not to
actively engage in any other employment,  occupation or consulting  activity for
any direct or indirect  remuneration  without  the prior  approval of the Board;
provided,  however,  that  Executive  may serve in any capacity  with any civic,
educational or charitable  organization,  or as a member of corporate  Boards of
Directors or committees thereof without the approval of the Board.

5. Employee Benefits. During the Full-Time Employment Period, Executive shall be
eligible  to  participate  in (i)  all  employee  benefit  plans  currently  and
hereafter  maintained  by the Company for senior  management  according to their
terms,  and (ii) such other  employee  benefits as are set forth in this Amended
Agreement.  During  any  Part-Time  Employment  Term,  Executive  shall  only be
eligible to participate in the Company's  group health,  vision and dental plans
and shall not be eligible to participate in the Company's other employee benefit
plans and arrangements.

6. Full-Time Employment Period Compensation.

a. Base Salary.  During the  Full-Time  Employment  Period,  and during  certain
Part-Time  Employment Terms as specified in Section 7 hereof,  the Company shall
pay the Executive as  compensation  for his services a base salary at an initial
annualized  rate  (which  initial  rate  shall  in no  event  be less  than  the
Executive's  current  base  salary  with  KLA  or  Tencor)  recommended  by  the
Compensation  Committee of the Board and approved by the Board, as adjusted from
time to time by the Board or its Compensation Committee (the "Base Salary"). The
Base Salary shall be paid periodically in accordance with normal Company payroll
practices and subject to the usual, required withholding. Base Salary shall mean
the last  full time  salary  as of the  beginning  of the  Part-Time  Employment
Period. During the Full-Time Employment Period, Executive's Base Salary shall be
reviewed annually for possible  adjustments in light of Executive's  performance
of his duties, as determined by the Board or its Compensation Committee.

b. Bonus.  During the Full-Time  Employment  Period and during certain Part-Time
Employment  Terms as specified in Section 7 hereof,  Executive shall be eligible
to receive bonuses as determined by the Board or its Compensation Committee. The
Company shall have the obligation to pay any and all bonuses referred to in this
Amended  Agreement  only at the same time as bonuses are normally paid to senior
management of the Company and contingent in each case upon the Company's payment
of bonuses to the senior officers of the Company in such fiscal year.

7. Termination of Employment; Transition to Part-Time Employment.

a. Part-Time Employment Term Definition;  Obligations.  The periods of part-time
employment  specified  in this  Section  7 shall be  defined  as the  "Part-Time
Employment  Term"  for  the  purposes  of this  Amended  Agreement.  During  any
Part-Time  Employment  Term,  Executive shall be required to devote such time in
rendering  services  to the  Company  as  shall  be  mutually  agreed  upon  and
acceptable  to the Executive  and the Company.  During the Part-Time  Employment
Term,  Executive shall be free to serve as a director,  employee,  consultant or
advisor to any other corporation or other business  enterprise without the prior
written  consent of the Company so long as such activities do not interfere with
his duties and  obligations  under this Amended  Agreement,  including,  without
limitation, Executive's obligations under Section 10 hereof. In consideration of
Executive's not working for a Non-Competing  Company or a Competing  Company and
being available to provide the mutually agreed upon services required  hereunder
during  the  Part-Time   Employment   Term,  the  Executive  shall  receive  the
compensation  specified  in  this  Section  7.  At  the  end of  such  Part-Time
Employment Term, the Executive's employment with the Company shall terminate.

b.  Termination of Full-Time  Employment for Cause.  The Company may at any time
terminate  Executive's  full-time  employment  hereunder  for  "Cause."  For the
purposes of this Amended  Agreement  "Cause"  shall mean (i)  Executive's  gross
negligence  or willful  misconduct  in connection  with the  performance  of his
duties, (ii) Executive's conviction of or plea of nolo contendere to, any felony
in a court of  competent  jurisdiction,  or (iii)  Executive's  embezzlement  or
misappropriation of Company property. If the Executive's full-time employment is
terminated by the Company for Cause,  then, subject to Executive entering into a
release of claims  agreement with the Company in a form  reasonably  approved by
the Company (the "Release"), the Executive will receive a lump-sum payment equal
to 25% of Base Salary and Executive  shall not be entitled to any other benefits
hereunder.


c.  Voluntary  Termination of Full-Time  Employment by Executive  Other than for
Good Reason.  If the Executive  desires to  voluntarily  terminate his full-time
employment  with the  Company,  then  Executive  shall  provide the Company with
written  notice of such  termination.  Subject to  Executive  entering  into the
Release,  the  Executive  shall  remain  employed  by the Company as a part-time
employee  on the terms  described  herein.  If such  notice is given (or  deemed
given) to the Company on or after April 30, 1998, the Part-Time  Employment Term
shall be 36 months.  During such 36-month  period,  Executive  shall be paid (A)
Base  Salary  for the first 24 months,  paid in  accordance  with the  Company's
normal payroll  practices,  (B) a mutually  agreeable level of compensation  per
month  (determined  based on the level of services  expected to be rendered) for
the final 12 months, paid monthly,  (C) an annual bonus equal to the amount that
would otherwise have been payable to Executive upon  Executive's  achievement of
100% of his  individual  bonus  objectives  (in  distinction  to  Company  bonus
objectives, which shall be based upon actual Company performance for such fiscal
year) for the Company's fiscal year in which Executive's transition to part-time
employment occurs (the "Target Bonus"), (D) for the Company's fiscal year ending
in the  period  between  the first  anniversary  of the date of  termination  of
Executive's  full-time  employment  and the  second  anniversary  of the date of
termination  of Executive's  full-time  employment  with the Company,  an amount
equal to the amount that would  otherwise  have been payable to  Executive  upon
Executive's   achievement  of  100%  of  his  individual  bonus  objectives  (in
distinction  to Company  bonus  objectives,  which  shall be based  upon  actual
Company  performance  for such fiscal year) under the  Company's  bonus plan for
such fiscal year (the "Second Year  Bonus"),  and (E) a pro-rated  bonus for the
Company's fiscal year in which Executive's  part-time employment terminates (the
"Part-Time  Employment  Termination  Fiscal Year") determined by multiplying the
amount that would  otherwise  have been  payable to Executive  upon  Executive's
achievement  of 100% of his  individual  bonus  objectives  (in  distinction  to
Company bonus objectives,  which shall be based upon actual Company  performance
for such fiscal year) for the Part-Time Employment  Termination Fiscal Year by a
fraction,  the  numerator  of  which  is the  number  of days  in the  Part-Time
Employment  Termination Fiscal Year covered by the Part-Time Employment Term and
the  denominator  of which is  three  hundred  and  sixty-five  (the  "Pro-Rated
Bonus").

d.  Termination of Full-Time  Employment by Company Other than for Cause. If the
Company desires to terminate  Executive's  full-time employment with the Company
other than for Cause,  then the Company  shall  provide  Executive  with written
notice  of  such  termination.   If  the  Executive's  full-time  employment  is
terminated  by the  Company  other than for Cause,  then,  subject to  Executive
entering into a Release,  the  Executive  shall receive the same benefits as set
forth in (c) above.

e. Reduction of Part-Time Employment Term Compensation and Benefits if Executive
Becomes Employed by a Non-Competing  Company. If during the Part-Time Employment
Term,  Executive becomes employed by an entity that is not a "Competing Company"
(as  defined in Section 10  hereof),  Executive  (i) shall have his Base  Salary
reduced to a mutually  agreeable amount per month (determined based on the level
of  services  expected  to be  rendered)  in exchange  for  Executive  providing
mutually  agreed  upon  services to the  Company,  (ii) shall not be eligible to
receive any Target Bonus, Second Year Bonus or Pro-Rated Bonus to the extent not
already  earned by Executive,  and (iii) shall not be eligible to participate or
receive benefits under any other employee benefit plans, policies,  practices or
arrangements  of the  Company  or its  predecessors.  For  the  purposes  of the
foregoing, the Target Bonus and Second Year Bonus shall be deemed earned, to the
extent otherwise  payable,  if Executive is a part-time  Employee of the Company
and is not  employed  by a  non-Competing  Company  through  the last day of the
fiscal  year to which such  bonuses  relate,  and the  Pro-Rated  Bonus shall be
deemed earned, to the extent otherwise payable, on the last day of the Part-Time
Employment Term if Executive is not employed by a non-Competing  Company through
the last day of the Part-Time Employment Term.

f. Stock Option Vesting During Part-Time  Employment Term.  During any Part-Time
Employment Term provided for in this Amended Agreement,  stock options that were
granted to  Executive  more than 12 months  prior to the  Executive's  full time
employment termination date ("Old Options") shall continue to vest in accordance
with the terms and conditions of the original option agreements relating to such
Old Options,  but any stock  options  granted to Executive  within the 12 months
prior to the Executive's  full time employment  termination date ("New Options")
shall not vest during the Part-Time  Employment Term. The term "stock option" as
used  herein does not include any right to  participate  in the  employee  stock
purchase  plans  of the  Company  or the  Prior  Companies,  which  right  shall
terminate immediately upon the commencement of any Part-Time Employment Period.

8.  Termination of Employment  Relationship.  Executive's  part-time  employment
relationship  with the Company may not be terminated by the Company prior to the
end of the  Part-Time  Employment  Term,  except (i) upon the death or permanent
disability of Executive,  (ii) by written  agreement between both of the parties
hereto; provided, however, that Executive's employment with the Company, whether
full-time or part-time,  shall  immediately  and  automatically  terminate  upon
Executive's breach of Section 10 hereof. No additional benefits or payments will
become  payable  to  Executive  hereunder  upon  a  termination  of  Executive's
Part-Time Employment Term.

9.  Death  or  Disability.  In the  event  of  Executive's  death  or  permanent
disability,  this Amended Agreement shall terminate, unless otherwise decided by
the Board.

10. Covenant Not to Compete.

a.  Covenant  Not to Compete.  During the  Full-Time  Employment  Period and the
Part-Time  Employment  Term,  Executive will not render services as an employee,
consultant,  director,  partner,  owner  to, or  participate  as more than a two
percent shareholder in, any Competing Company in a Restricted Territory, as such
terms are defined immediately below.

b.  Competing  Company.  "Competing  Company"  shall mean another  semiconductor
capital equipment company,  partnership,  limited liability corporation or other
entity  any  portion  of  whose   business,   including,   without   limitation,
development,  manufacturing,  marketing,  sales or technical  or sales  support,
competes with the Company's business at that time.


c. Restricted Territory. "Restricted Territory" means any county in the State of
California, each state in the United States and each country in the world.

11.  Limitation  on  Payments.  If the  benefits  provided  for in this  Amended
Agreement  or  otherwise  payable to the  Executive  (i)  constitute  "parachute
payments"  within the meaning of Section  280G of the  Internal  Revenue Code of
1986, as amended (the "Code") and (ii) but for this Section 11, would be subject
to the excise tax  imposed by  Section  4999 of the Code,  then the  Executive's
benefits  hereunder  shall be either (i) delivered in full, or (ii) delivered as
to such  lesser  extent  which,  or at such  later time as,  would  result in no
portion of such  severance  benefits  being  subject to excise tax under Section
4999 of the Code,  whichever of the foregoing  amounts,  taking into account the
applicable  federal,  state and local income taxes and the excise tax imposed by
Section 4999,  results in the receipt by the Executive on an after-tax basis, of
the greatest  amount of  severance  benefits,  notwithstanding  that all or some
portion of such benefits may (or might  otherwise) be taxable under Section 4999
of the Code.  Unless the Company and the Executive  otherwise  agree in writing,
any determination required under this Section 11 shall be made in writing by the
Company's   independent   public   accountants   (the   "Accountants"),    whose
determination shall be conclusive and binding upon the Executive and the Company
for all  purposes;  provided  that if  benefits  are  reduced or  deferred,  the
Executive shall choose the order in which such benefits are reduced or deferred.
For  purposes  of making  the  calculations  required  by this  Section  11, the
Accountants  may  make  reasonable  assumptions  and  approximations  concerning
applicable  taxes  and  may  rely  on  reasonable,  good  faith  interpretations
concerning  the  application  of Sections 280G and 4999 of the Code. The Company
and  the  Executive  shall  furnish  to the  Accountants  such  information  and
documents  as  the  Accountants  may  reasonably  request  in  order  to  make a
determination  under  this  Section.  The  Company  shall  bear  all  costs  the
Accountants   may  reasonably   incur  in  connection   with  any   calculations
contemplated by this Section 11.

12. Assignment.  Executive's rights and obligations under this Amended Agreement
shall not be assignable by Executive. The Company's rights and obligations under
this Amended Agreement shall not be assignable by the Company except as incident
to the transfer, by merger,  liquidation,  or otherwise, of all or substantially
all of the business of the Company.

13. Notices. Any notice required or permitted under this Amended Agreement shall
be given in writing and shall be deemed to have been  effectively  made or given
if personally delivered,  or if sent by facsimile, or mailed or sent via Federal
Express to the other party at its address set forth below in this Section 13, or
at such other address as such party may designate by written notice to the other
party hereto.  Any effective  notice hereunder shall be deemed given on the date
personally delivered or on the date sent by facsimile or deposited in the United
States mail (sent by certified mail, return receipt requested),  as the case may
be, at the following addresses:


                  If to the Company:        KLA-Tencor Corporation
                                            160 Rio Robles
                                            San Jose, CA 95134
                              Attn: General Counsel

                  If to Executive:  Kenneth Levy
                                            19800 Glen Una Drive
                                            Saratoga, CA 95070

14.  Arbitration.  The  parties  hereto  agree that any  dispute or  controversy
arising out of,  relating to, or in connection with this Amended  Agreement,  or
the interpretation,  validity, construction, performance, breach, or termination
thereof,  shall be finally  settled by binding  arbitration  to be held in Santa
Clara County,  California under the Employment  Dispute  Resolution Rules of the
American  Arbitration   Association  as  then  in  effect  (the  "Rules").   The
arbitrator(s)  may  grant  injunctions  or  other  relief  in  such  dispute  or
controversy.  The decision of the arbitrator(s)  shall be final,  conclusive and
binding on the parties to the  arbitration,  and  judgment may be entered on the
decision of the arbitrator(s) in any court having jurisdiction.

The  arbitrator(s)  shall apply  California  law to the merits of any dispute or
claim,  without  reference to rules of  conflicts  of law,  and the  arbitration
proceedings  shall be  governed  by  federal  arbitration  law and by the Rules,
without reference to state arbitration law.

The  parties  shall  each  pay  one-half  of the  costs  and  expenses  of  such
arbitration, and each party shall pay its own counsel fees and expenses.

EXECUTIVE HAS READ AND UNDERSTANDS THIS SECTION 14, WHICH DISCUSSES ARBITRATION.
EXECUTIVE  UNDERSTANDS THAT BY SIGNING THIS AMENDED AGREEMENT,  EXECUTIVE AGREES
TO SUBMIT ANY CLAIMS  ARISING OUT OF,  RELATING TO, OR IN  CONNECTION  WITH THIS
AMENDED AGREEMENT, OR THE INTERPRETATION,  VALIDITY, CONSTRUCTION,  PERFORMANCE,
BREACH OR TERMINATION THEREOF TO BINDING ARBITRATION,  AND THAT THIS ARBITRATION
CLAUSE  CONSTITUTES A WAIVER OF EXECUTIVE'S RIGHT TO A JURY TRIAL AND RELATES TO
THE  RESOLUTION OF ALL DISPUTES  RELATING TO EXECUTIVE'S  RELATIONSHIP  WITH THE
COMPANY.

15.  Withholding.  The Company  shall be entitled  to  withhold,  or cause to be
withheld,  from  payment any amount of  withholding  taxes  required by law with
respect  to  payments  made to  Executive  in  connection  with  his  employment
hereunder.


16.  Severability.  If any term or provision of this Amended  Agreement shall to
any extent be declared  illegal or  unenforceable  by arbitrator(s) or by a duly
authorized court of competent  jurisdiction,  then the remainder of this Amended
Agreement or the  application of such term or provision in  circumstances  other
than those as to which it is so declared illegal or unenforceable,  shall not be
affected  thereby,  each term and provision of this Amended  Agreement  shall be
valid and enforceable to the fullest extent  permitted by law and the illegal or
unenforceable. term or provision shall be deemed replaced by a term or provision
that is valid and enforceable and that comes closest to expressing the intention
of the invalid or unenforceable term of provision.

17. Entire Agreement.  This Amended Agreement and the agreements relating to the
New Options and Old Options  represent the entire  agreement of the parties with
respect to the matters set forth  herein,  and to the extent  inconsistent  with
other prior  contracts,  arrangements  or  understandings  between the  parties,
supersedes all such previous contracts,  arrangements or understandings  between
the Company and Executive. The Amended Agreement may be amended at any time only
by mutual written agreement signed by the parties hereto.

18. Governing Law. This Amended Agreement shall be construed,  interpreted,  and
governed  in  accordance  with  the  laws of the  State  of  California  without
reference  to rules  relating  to  conflict  of law  (other  than any such rules
directing application of California law).

19.  Headings.   The  headings  of  sections  herein  are  included  solely  for
convenience of reference and shall not control the meaning or  interpretation of
any of the provisions of this Amended Agreement.

20.  Counterparts.  This  Amended  Agreement  may be  executed  by either of the
parties hereto in counterparts, each of which shall be deemed to be an original,
but all such counterparts shall together constitute one and the same instrument.


EXECUTIVE                                   KLA-TENCOR CORPORATION



/s/ KENNETH LEVY                           /s/  ARTHUR P, SCHNITZER
- ----------------                           -------------------------
Kenneth Levy                                 Arthur P. Schnitzer
                                             Executive Vice President,
                                             Human Resources

Date: April 29, 1998