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                                   Exhibit 3.1
                AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

                                       OF

                           KLA INSTRUMENTS CORPORATION


         KLA Instruments Corporation, a corporation organized and existing
under the laws of the State of Delaware, hereby certifies as follows:

         1.      The name of the corporation is KLA Instruments Corporation,
and the name under which the corporation was originally incorporated is KLA
Corporation.  The date of filing its original Certificate of Incorporation with
the Secretary of State was July 9, 1975.

                 The amendment to the corporation's Certificate of
Incorporation set forth was approved by the corporation's Board of Directors
and stockholders and was duly adopted in accordance with the provisions of
Sections 242 and 245 of the General Corporation Law of the State of Delaware.

         2.      The text of the Certificate of Incorporation as amended or
supplemented heretofore is hereby amended and restated to read as herein set
forth in full:
         "FIRST:  The name of the corporation (hereinafter called the
"corporation") is KLA-Tencor Corporation.

         SECOND:  The address, including street, number, city and county, of
the registered office of the corporation in the State of Delaware is 1209
Orange Street, City of Wilmington, County of New Castle, and the name of the
registered agent of the corporation in the State of Delaware at such address is
The Corporation Trust Company.

         THIRD:  The nature of the business and of the purposes to be conducted
and promoted by the corporation is as follows:

         To manufacture, purchase or otherwise acquire, import and export,
invest in, own, mortgage, pledge, sell, assign, and transfer or otherwise
dispose of, trade, deal in and deal with goods, wares, merchandise and personal
property of every kind, nature and description, both on its own account and for
others.
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         To render services of every kind, nature and description (including,
but not limited to, consulting, financial, engineering, research and similar or
related services) both on its own account and for others.

         To develop, obtain, purchase or otherwise acquire, and to hold, own,
use, sell, limit or otherwise dispose of processes, formulae, inventions and
devices of every kind, nature and description, whether patented or not; and to
apply for and obtain letters patent under the laws of the United States or of
any foreign country.

         To borrow or lend money, and to make and issue notes, bonds,
debentures, obligations, and evidences of indebtedness of all kinds, whether
secured by mortgage, pledge, or otherwise, without limit as to amount, and to
secure the same by mortgage, pledge, or otherwise and generally to make and
perform agreements and contracts of every kind and description.

         To subscribe for, take, acquire, hold, sell, exchange and deal in
shares, stock, bonds, obligations and securities of any corporation,
government, authority or company; to form, promote, subsidize and assist
companies, syndicates, or partnerships of all kinds, and to finance and
refinance the same; and to guarantee the obligations of other persons, firms,
or corporations.

         In general, to do any act necessary or incidental to the conduct of
said businesses and in the transaction thereof, to carry on any other business,
whether manufacturing or otherwise, and to do any other thing permitted by all
present and future laws of the State of Delaware applicable to business
corporations.

         FOURTH:  The aggregate number of shares of stock which the corporation
shall have authority to issue shall be 251,000,000 shares, with the par value
of each of such shares being $0.001.  These shares shall be divided into the
following classes:

         (1)     250,000,000 shares shall be designated as Common Stock; and

         (2)     1,000,000 shares shall be designated as Preferred Stock.

         The Board of Directors is authorized, subject to any limitations
prescribed by law, to provide for the issuance of shares of Preferred Stock in
series, and by filing a certificate pursuant to the applicable law of the State
of Delaware, to establish from time to time the number of shares to be included
in each such series, and to fix the designation, powers, preferences, and
rights of the shares of each such series and any qualifications, limitations or
restrictions thereof.  The number of authorized shares of Preferred Stock may
be increased or decreased (but not below the number of shares thereof then
outstanding) by the affirmative vote of the holders of a majority of the then
outstanding shares of Common Stock, without a vote of the holders of the
Preferred Stock, or of any series thereof, unless a vote of any such holders is
required pursuant to the certificate or certificates establishing the series of
Preferred Stock.

         FIFTH:  The name and the mailing address of the incorporator are as
follows:











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               Name                           Mailing Address
       ---------------------                ---------------------
         R.G. Dickerson                          229 South State Street
                                                 Dover, Delaware

         SIXTH:  The corporation is to have perpetual existence.

         SEVENTH:  Whenever a compromise or arrangement is proposed between
this corporation and its creditors or any class of them and/or between this
corporation and its stockholders or any class of them, any court of equitable
jurisdiction with the State of Delaware may, on the application in a summary
way of this corporation or of any creditor or stockholder thereof or on the
application of any receiver or receivers appointed for this corporation under
the provisions of Section 291 of Title 8 of the Delaware Code or on the
application of trustees in dissolution or of any receiver or receivers
appointed for this corporation under the provisions of Section 279 of Title 8
of the Delaware Code order a meeting of the creditors or class of creditors,
and/or of the stockholders or class of stockholders of this corporation, as the
case may be, to be summoned in such manner as the said court directs.  If a
majority in number representing three-fourths in value of the creditors or
class of creditors and/or of the stockholders or class of stockholders of this
corporation; as the case may be, agree to any compromise or arrangement and to
any reorganization of this corporation as consequence of such compromise or
arrangement, the said compromise or arrangement and the said reorganization
shall, if sanctioned by the court to which the said application has been made,
be binding on all the creditors or class of creditors, and/or on all the
stockholders or class of stockholders, of this corporation, as the case may be,
and also on this corporation.

         EIGHTH:  For the management of the business and for the conduct of the
affairs of the corporation, and in further definition, limitation and
regulation of the powers of the corporation and of its directors and of its
stockholders or any class thereof, as the case may be, it is further provided:

         1.      (a)  The business and affairs of the corporation shall be
managed by or under the direction of the Board of Directors.  In addition to
the powers and authority expressly conferred upon them by the General
Corporation Law of the State of Delaware or by this Certificate of
Incorporation or the By-Laws of the corporation, the directors are hereby
empowered to exercise all such powers and do all such acts and things as may be
exercised or done by the corporation.

                 (b)      The number of directors shall initially be 6 and,
thereafter, shall be fixed from time to time exclusively by the Board of
Directors pursuant to a resolution adopted by a majority of the total number of
authorized directors (whether or not there exist any vacancies in previously
authorized directorships at the time any such resolution is presented to the
Board for adoption).

                 (c)      The directors shall be divided into three classes, as
nearly equal in number as reasonably possible, with the term of office of the
first class to expire at the 1990 annual meeting of stockholders, the term of
office of the second class to expire at the 1991 annual meeting of stockholders
and the term of office of the third class to expire at the 1992 annual meeting
of





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stockholders.  At each annual meeting of stockholders following such initial
classification and election, directors shall be elected to succeed those
directors whose terms expires for a term of office to expire at the third
succeeding annual meeting of stockholders after their election.  All directors
shall hold office until the expiration of the term for which elected, and until
their respective successors are elected, except in the case of the death,
resignation, or removal of any director.

                 (d)      Subject to the rights of the holders of any series of
Preferred Stock then outstanding, newly created directorships resulting from
any increase in the authorized number of directors or any vacancies in the
Board of Directors resulting from death, resignation, retirement,
disqualification or other cause (other than removal from office by a vote of
stockholders) may be filled only by a majority vote of the directors then in
office, though less than a quorum, and directors so chosen shall hold office
for a term expiring at the annual meeting of stockholders at which the term of
office of the class to which they have been elected expires.  No decrease in
the number of directors constituting the Board of Directors shall shorten the
term of any incumbent director.

                 (e)      Subject to the rights of the holders of any series of
Preferred Stock then outstanding, any directors, or the entire Board of
Directors, may be removed from office at any time, but only for cause and only
by the affirmative vote of the holders of at least a majority of the voting
power of all of the then outstanding shares of capital stock of the corporation
entitled to vote generally in the election of directors, voting together as a
single class.  Vacancies in the Board of Directors resulting from such removal
may be filled by (i) a majority of the directors then in office, though less
than a quorum, or (ii) the stockholders at a special meeting of the
stockholders properly called for that purpose, by the vote of the holders of a
majority of the shares entitled to vote at such special meeting.  Directors so
chosen shall hold office for a term expiring at the annual meeting of
stockholders at which the term of office of the class to which they have been
elected expires.

         2.      After the original or other By-Laws of the corporation have
been adopted, amended, or repealed, as the case may be, in accordance with the
provisions of Section 109 of the General Corporation Law of the State of
Delaware, and, after the corporation has received any payment for any of its
stock, the power to adopt, amend, or repeal the By-Laws of the corporation may
be exercised by the Board of Directors of the corporation.

         3.      Whenever the corporation shall be authorized to issue only one
class of stock, each outstanding share shall entitle the holder thereof to
notice of, and the right to vote at, any meeting of stockholders.  Whenever the
corporation shall be authorized to issue more than one class of stock, no
outstanding share of any class of stock which is denied voting power under the
provisions of the certificate of incorporation shall entitle the holder thereof
to the right to vote, at any meeting of stockholders except as the provisions
of paragraph (c)(2) of Section 242 of the General Corporation Law of the State
of Delaware shall otherwise require; provided, that no share of any such class
which is otherwise denied voting power shall entitle the holder thereof to vote
upon the increase or decrease in the number of authorized shares of said class.





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         4.      Any action required or permitted to be taken by the
stockholders of the corporation must be effected at a duly called annual or
special meeting of stockholders of the corporation and may not be effected by
any consent in writing by such stockholders.

         NINTH:  The corporation shall, to the fullest extent permitted by
Section 145 of the General Corporation Law of the State of Delaware, as the
same may be amended and supplemented, indemnify any and all persons whom it
shall have power to indemnify under said section from and against any and all
of the expenses, liabilities and other matters referred to in or covered by
said section, and the indemnification provided for herein shall not be deemed
exclusive of any other rights to which those indemnified may be entitled under
any By-Law, agreement, vote of stockholders or disinterested directors or
otherwise, both as to action in his official capacity and as to action in
another capacity while holding such office, and shall continue as to a person
who has ceased to be a director, officer, employee or agent and shall inure to
the benefit of the heirs, executors and administrators of such a person.

         TENTH:  From time to time any of the provisions of this certificate of
incorporation may be amended, altered or repealed, and other provisions
authorized by the laws of the State of Delaware at the time in force may be
added or inspected in the manner and at the time prescribed by said laws, and
all rights at any time conferred upon the stockholders of the corporation by
this certificate of incorporation are granted subject to the provisions of this
Article TENTH.

         ELEVENTH:

                 1.       (a)     In addition to any affirmative vote required
by law or this certificate of incorporation, and except as otherwise expressly
provided in paragraph 2 of this Article ELEVENTH:

                                  (i)      any merger or consolidation of the
corporation or any Subsidiary (as hereinafter defined) with (a) any Interested
Shareholder (as hereinafter defined) or (b) any other corporation (whether or
not itself an Interested Shareholder) which is, or after such merger or
consolidation would be, an Affiliate (as hereinafter defined) of an Interested
Shareholder; or

                                  (ii)     any sale, lease, exchange, mortgage,
pledge, transfer or other disposition (in one transaction of a series of
transactions) to or with any Interested Shareholder or any Affiliate of any
Interested Shareholder of any assets of the corporation or any Subsidiary
having an aggregate fair market value of $1,000,000 or more; or

                                  (iii)    the issuance or transfer by the
corporation or any Subsidiary (in one transaction or a series of transactions)
of any securities of the corporation or any Subsidiary to any Interested
Shareholder or any Affiliate of any Interested Shareholder in exchange for
cash, securities or other property (or a combination thereof) having an
aggregate fair market value of $1,000,000 or more; or





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                                  (iv)     the adoption of any plan or proposal
for the liquidation or dissolution of the corporation proposed by or on behalf
of an Interested Shareholder or any Affiliate of any Interested Shareholder; or

                                  (v)      any reclassification of securities
(including any reverse stock split), or recapitalization of the corporation, or
any merger or consolidation of the corporation with any of its subsidiaries or
any other transaction (whether or not with or into or otherwise involving an
Interested Shareholder) which has the effect, directly or indirectly, of
increasing the proportionate share of the outstanding shares of any class of
equity or convertible securities of the corporation or any Subsidiary which is
directly or indirectly owned by an Interested Shareholder or any Affiliate of
any Interested Shareholder; shall require the affirmative vote of the holders
of at least 80% of the then outstanding shares of capital stock of the
corporation authorized to be issued from time to time under Article FOURTH of
this certificate of incorporation (the "Voting Stock"), voting together as a
single class.  Such affirmative vote shall be required notwithstanding the fact
that no vote may be required, or that a lesser percentage may be specified, by
law or in any agreement with any national securities exchange or otherwise.
Notwithstanding any other provision of this certificate of incorporation to the
contrary, for purposes of this Article ELEVENTH, each share of the Voting Stock
shall have one vote.

                          (b)     The term "Business Combination" as used in
this Article ELEVENTH shall mean any transaction which is referred to in any
one or more of clauses (i) through (v) of subparagraph (a) of this paragraph 1.

         2.      The provisions of paragraph 1 of this Article ELEVENTH shall
not be applicable to any particular Business Combination, and such Business
Combination shall require only such affirmative vote as if required by law and
any other provision of this certificate of incorporation, if all of the
conditions specified in the following subparagraph (a) are met:

                 (a)      The Business Combination shall have been approved by
a majority of the Continuing Directors (as hereinafter defined): provided,
however, that such approval shall only be effective if obtained at a meeting at
which a Continuing Director Quorum (as hereinafter defined) is present.

         3.      For the purposes of this Article ELEVENTH:

                 (a)      The term "person" shall mean any individual, firm,
corporation or other entity.

                 (b)      The term "Interested Shareholder" shall mean any
person (other than the corporation or any Subsidiary and other than any
profit-sharing, employee stock ownership or other employee benefit plan of the
corporation or any Subsidiary or any trustee of or fiduciary with respect to
any such plan when acting in such capacity) who or which:

                          (i)     is the beneficial owner (as hereinafter
defined) of more than five percent of the Voting Stock; or





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                          (ii)    is an Affiliate (as hereinafter defined) of
the corporation and at any time within the two-year period immediately prior to
the date in question was the beneficial owner of five percent or more of the
Voting Stock; or

                          (iii)   is an assignee of or has otherwise succeeded
to any shares of Voting Stock which were at any time within the two-year period
immediately prior to the date in question beneficially owned by any Interested
Shareholder, if such assignment or succession shall have occurred in the course
of a transaction or series of transactions not involving a public offering
within the meaning of the Securities Act of 1933, as amended.

                 (c)      A person shall be a "beneficial owner" of any Voting
Stock:

                          (i)     which such person or any of its Affiliates or
Associates (as hereinafter defined) beneficially owns, directly or indirectly;
or

                          (ii)    which such person or any of its Affiliates or
Associates has, directly or indirectly, (a) the right to acquire (whether such
right is exercisable immediately or only after the passage of time), pursuant
to any agreement, arrangement or understanding or upon the exercise of
conversion rights, exchange rights, warrants or options, or otherwise, or (b)
the right to vote pursuant to any agreement, arrangement or understanding; or

                          (iii)   which are beneficially owned, directly or
indirectly, by any other person with which such person or any of its Affiliates
or Associates has any agreement, arrangement or understanding for the purpose
of acquiring, holding, voting or disposing of any shares of Voting Stock.

                 (d)      For the purposes of determining whether a person is
an Interested Shareholder pursuant to subparagraph (b) of this paragraph 3, the
number of shares of Voting Stock deemed to be outstanding shall include shares
deemed owned through application of subparagraph (c) of this paragraph 3 may be
issuable pursuant to any agreement, arrangement or understanding, or upon
exercise of conversion rights, warrants or options, or otherwise.

                 (e)      The terms "Affiliate" or "Associate" shall have the
respective meanings ascribed to such terms in Rule 12b-2 of the General Rules
and Regulations under the Securities Exchange Act of 1934, as in effect on
January 1, 1984.

                 (f)      The term "Subsidiary" means any corporation of which
a majority of any class of equity security is owned, directly  or indirectly,
by the corporation; provided, however,  that for the purposes of the definition
of Interested Shareholder set forth in subparagraph (b) of this paragraph 3,
the term "Subsidiary" shall mean only a corporation of which a majority of each
class of equity security is owned, directly or indirectly, by the corporation.

                 (g)      The term "Continuing Director" means any member of
the Board of Directors of the corporation (the "Board") who is unaffiliated
with the Interested Shareholder and was a





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member of the Board prior to the time that the Interested Shareholder became an
Interested Shareholder, and any successor of a Continuing Director who is
unaffiliated with the Interested Shareholder or is recommended or elected to
succeed a Continuing Director by a majority of Continuing Directors, provided
that such recommendation or election shall only be effective if made at a
meeting at which a Continuing Director Quorum is present.

                 (h)      The term "Continuing Director Quorum" means four
Continuing Directors capable of exercising the powers conferred upon them under
the provisions of the certificate of incorporation or By-Laws of the
corporation or by law.

         4.      Notwithstanding any other provisions of this certificate of
incorporation or the By-Laws of the corporation (and notwithstanding the fact
that a lesser percentage may be specified by law, this certificate of
incorporation or the By-Laws of the corporation), the affirmative vote of the
holders of 80% or single class, shall be required to amend or repeal, or adopt
any provisions inconsistent with, this Article ELEVENTH.

         TWELFTH:  A director of this corporation shall not be personally
liable to the corporation or its stockholders for monetary damages for breach
of fiduciary duty as a director, except for liability (i) for any breach of the
director's duty of loyalty to the corporation or its stockholders, (ii) for
acts or omissions not in good faith of which involve intentional misconduct or
a knowing violation of law, (iii) under Section 174 of the Delaware General
Corporation Law, or (iv) for any transaction from which the director derived an
improper personal benefit.

         If the Delaware General Corporation Law is hereafter amended to
authorize the further elimination or limitation of the liability of a director,
then the liability of a director of the corporation shall be eliminated or
limited to the fullest extent permitted by the Delaware General Corporation
Law, as so amended.

         Any repeal or modification of the foregoing provisions of this Article
TWELFTH by the stockholders of the corporation shall not adversely affect any
right or protection of a director of the corporation existing at the time of
such repeal or modification."





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         IN WITNESS WHEREOF, said KLA Instruments Corporation has caused this
certificate to be signed by Kenneth Levy, its Chief Executive Officer, and
attested by Larry W. Sonsini, its Secretary, this 30th day of April, 1997.

                                    KLA INSTRUMENTS CORPORATION


                                    By:      /s/ Kenneth Levy
                                             ---------------------------------
                                             Kenneth Levy
                                             Chief Executive Officer


ATTEST:


By:      /s/ Larry W. Sonsini
         ------------------------------------------
         Larry W. Sonsini
         Secretary


























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