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                                                                     EXHIBIT 3.1


                AMENDED AND RESTATED CERTIFICATE OF INCORPORATION
                             OF KOMAG, INCORPORATED,
                             A DELAWARE CORPORATION

      The undersigned, T.H. Tan and Edward H. Siegler, hereby certify that:

      FIRST:    They are the duly elected and acting President and Secretary,
respectively, of said corporation.

      SECOND:   The Certificate of Incorporation of said corporation was
originally filed with the Secretary of State of Delaware on October 29, 1986
under the name Komag Delaware, Inc.

      THIRD:    Pursuant to Sections 242 and 245 of the General Corporation Law
of the State of Delaware, the Certificate of Incorporation of said corporation
shall be amended and restated to read in full as follows.

      FOURTH:   The Plan of Reorganization, dated September 20, 2001, of the
corporation has been confirmed by the United States Bankruptcy Court for the
Northern District of California and has become effective in accordance with its
terms:

                                    ARTICLE I

      The name of the corporation (herein called the "Corporation") is Komag,
Incorporated.

                                   ARTICLE II

      The address of the registered office of the Corporation in the State of
Delaware is Corporation Trust Center, 1209 Orange Street, in the City of
Wilmington, County of New Castle, zip code 19801. The name of the registered
agent of the Corporation at such address is The Corporation Trust Company.

                                   ARTICLE III

      The purpose of the Corporation is to engage in any lawful act or activity
for which corporations may be organized under the General Corporation Law of the
State of Delaware.

                                   ARTICLE IV

      The Corporation shall be authorized to issue Fifty Million (50,000,000)
shares of capital stock having an aggregate par value of Five Hundred Thousand
Dollars ($500,000). This Capital Stock shall consist entirely of Common Stock
having a par value. The authorized Common Stock shall be Fifty Million shares
(50,000,000) shares having a par value of one cent ($.01) per share for an
aggregate class par value of Five Hundred Thousand Dollars ($500,000). The
Corporation is also


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authorized to issue debentures (convertible into the Common Stock or
non-convertible, either with or without voting rights) and/or warrants or
options to purchase Common Stock.

                                    ARTICLE V

      In the furtherance and not in limitation of the powers conferred by
statute, the Board of Directors is expressly authorized to make, alter, amend or
repeal the By-Laws of the Corporation.

                                   ARTICLE VI

      The number of directors of the Corporation shall be fixed from time to
time by a by-law or amendment thereof duly adopted by the Board of Directors or
by the stockholders.

                                   ARTICLE VII

      The Corporation shall not issue any non-voting equity securities. All
rights to vote and all voting power shall be vested in the Common Stock.

      The Board of Directors shall be divided into three classes, the members of
each class to serve for a term of three years; provided that the directors shall
be elected as follows: at the first annual meeting of the stockholders after the
date hereof, the directors in the first class shall be elected for a term of
three years, at the second annual meeting after the date hereof, the directors
in the second class shall be elected for a term of three years, and at the third
annual meeting after the date hereof, the directors in the third class shall be
elected for a term of three years. The Board of Directors by resolution shall
nominate the directors to be elected for each class. At subsequent annual
meetings of stockholders, a number of directors shall be elected equal to the
number of directors with terms expiring at that annual meeting. Directors
elected at each such subsequent annual meeting shall be elected for a term
expiring with the annual meeting of stockholders three years thereafter. If the
number of directors is changed, any increase or decrease shall be apportioned
among the classes so as to maintain the number of directors in each class as
nearly equal as possible, and any additional director of any class elected to
fill a vacancy resulting from an increase in such class shall hold office for a
term that shall coincide with the remaining term of that class, but in no case
will a decrease in the number of directors shorten the term of any incumbent
director.

                                  ARTICLE VIII

      Elections of directors need not be by written ballot unless the By-laws of
the Corporation shall so provide.

                                   ARTICLE IX

      Meetings of stockholders may be held within or without the State of
Delaware, as the By-laws may provide. The books of the Corporation may be kept
(subject to any provision contained in the statutes) outside the State of
Delaware at such place or places as may be designated from time to time by the
Board of Directors or in the By-laws of the Corporation.


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                                    ARTICLE X

      A director of the 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 or which involve intentional misconduct or knowing
violation of law, (iii) under Section 174 of the Delaware General Corporation
Law, or (iv) for any transaction from which the director derived any improper
personal benefit.

                                   ARTICLE XI

      The Corporation reserves the right to amend, alter, change or repeal any
provision contained in this restated Certificate of Incorporation, in the manner
now or hereafter prescribed by statute, and all rights conferred upon
stockholders herein are granted subject to this reservation.

                                   ARTICLE XII

      The Corporation reserves the right to amend, alter, change or repeal any
provision contained in this Amended and Restated Certificate of Incorporation,
in the manner now or hereafter prescribed by statue, and all rights conferred
upon stockholders herein are granted subject to this reservation.

                                  ARTICLE XIII

      The Corporation shall have perpetual existence.

      FIFTH: The foregoing Amended and Restated Certificate of Incorporation has
been duly adopted by the Corporation's Board of Directors and stockholders in
accordance with the applicable provisions of Sections 242 and 245 of the General
Corporation Law of the State of Delaware. The foregoing Amended and Restated
Certificate of Incorporation has been adopted pursuant to the Plan of
Reorganization of the Company dated September 20, 2001.

      IN WITNESS WHEREOF, the undersigned have executed this certificate on
_______, 2002.

                                        KOMAG, INCORPORATED



                                        By:
                                           -------------------------------------
                                           T. H. Han, President

Attest:
       ----------------------------
       Edward H. Siegler, Secretary


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