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                                                                   EXHIBIT 10.28




                       CABOT MICROELECTRONICS CORPORATION

                      DIRECTORS' DEFERRED COMPENSATION PLAN


                          ADOPTED AS OF MARCH 13, 2001




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                       CABOT MICROELECTRONICS CORPORATION
                       DIRECTORS' DEFERRED COMPENSATION PLAN

         Cabot Microelectronics Corporation (the "Company") desires to establish
a Directors' Deferred Compensation Plan (the "Plan") to assist the Company in
attracting and retaining persons of competence and stature to serve as Directors
by giving those Directors the option of deferring receipt of the fees payable to
them by the Company for their services as Directors and creating an opportunity
for appreciation of fees deferred based on appreciation of the Company's Common
Shares.

         Therefore, the Company hereby adopts the Plan as hereinafter set forth:

         1. EFFECTIVE DATE. The Plan is effective as of the date of its adoption
by the Board of Directors of the Company.

         2. PARTICIPATION. Each Director of the Company who: (a) is duly elected
to the Company's Board of Directors; and (b) receives fees for services as a
Director, is an "Eligible Director." Each Eligible Director may elect to defer
receipt of fees otherwise payable to that Eligible Director, as provided for in
the Plan. Each Eligible Director who elects to defer fees will be a Participant
in the Plan.

         3. ADMINISTRATION. The Company's Board of Directors appoints Matthew
Neville and H. Carol Bernstein to act as the Administrators of the Plan (the
"Administrator"). The Administrators will serve at the pleasure of the Board of
Directors and will administer, construe and interpret the Plan. The
Administrators will not be liable for any act done or determination made in good
faith. The Board of Directors has the power to designate additional or
replacement Administrators at its discretion. The expense of administering the
Plan shall be borne by the Company and shall not be charged against benefits
payable hereunder.


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         4. DEFERRALS.

            (A) DEFERRAL ELECTION. An Eligible Director may file with the
Administrator prior to December 1 of each year an election in writing to
participate in the Plan and to defer all or a portion of the fees otherwise
payable to the Eligible Director for succeeding periods (a "Deferral Election").
Upon adoption of the Plan, Eligible Directors may elect to defer fees otherwise
payable for the fiscal quarter during which the Plan was adopted and subsequent
periods by making a Deferral Election. Each Eligible Director who first becomes
eligible to participate after the date of the adoption of the Plan may make a
Deferral Election for the portion of the year in which the Eligible Director
first became eligible with respect to fees to be received after the date of that
election. When a Deferral Election is filed, an amount equal to all or a portion
(as designated in the Deferral Election) of the fees otherwise payable to a
Participant for succeeding periods (as designated in the Deferral Election) will
be credited to a deferral account maintained on behalf of that Participant (the
"Deferral Account"). A Deferral Election must also state a distribution
commencement date as provided under paragraph 5, and a method of distribution
(lump sum or equal annual installments). If a Deferral Election has been filed
to participate in the Plan for succeeding periods and a Participant wishes to
discontinue such deferrals, an election in writing to terminate participation in
the Plan for any subsequent period must be filed with the Administrators prior
to the beginning of such period.

            (B) MINIMAL DEFERRAL. The amount of Deferral Election may not be
less than $1,000 per calendar quarter.

            (C) ACCOUNTING. The Deferral Accounts will be maintained by the
Company and will list and reflect each Participant's credits and valuations. The
Administrator will provide each Participant an annual statement of the balance
in that Participant's Deferral Account. The





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Company will credit to each Participant's Deferral Account an amount equivalent
to the fees or portion of those fees, that would have been paid to the
Participant if the Participant had not elected to participate in the Plan. The
credit will be made on the date on which the fee would have been paid absent a
Deferral Election. No funds will be segregated into the Deferral Account of
Participants.

            (D) VALUATION. Until the first distribution to a Participant,
amounts credited to a Deferral Account of that Participant will be increased or
decreased as measured by the market value of the Company's Common Shares plus
the value of dividends or other distributions on the Company's Common Shares.
Each amount credited to a Deferral Account will be assigned a number of Share
Units (including fractions thereof) determined by dividing the amount credited
to the Deferral Account, whether in lieu of payment of fees for service as a
director or as a dividend or other distribution attributable to those Share
Units, by the Fair Market Value of the Company's Common Shares (as defined
below) on the date of credit. Fair Market Value of the Company's Common Shares
means: (i) the closing price of the Company's Common Shares on the principal
exchange on which the Company's Common Shares are then trading, if any, on the
date of credit, or, if shares were not traded on the date of credit, then on the
next preceding trading day during which a sale occurred; or (ii) if the Common
Shares are not traded on an exchange but are quoted on the Nasdaq National
Market System or a successor quotation system, (1) the last sales price (if the
Common Shares are then listed as a National Market Issue under Nasdaq), or (2)
the mean between the closing representative bid and asked prices for the Common
Shares on the date of credit as reported by Nasdaq or a successor quotation
system, or (iii) if the Common Shares are not publicly traded on an exchange and
not quoted on Nasdaq or a successor quotation system the mean between the
closing bid and asked prices for the Common


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Shares on the date of credit, as determined in good faith by the Company's Chief
Financial Officer; or (iv) if the Company's Common Shares are not publicly
traded, the fair market value established by the Company's Chief Financial
Officer acting in good faith. Each Share Unit will have the value of a Common
Share of the Company. The number of Share Units will be adjusted to reflect
stock splits, stock dividends or other capital adjustments effected without
receipt of consideration by the Company.

         5. DISTRIBUTION. A Participant must elect in writing, at the time each
Deferral Election is made under subparagraph 4(a), the date on which
distribution of the amounts credited to the Participant's Deferral Account to
which that Deferral Election relates will commence and the method of
distribution, as permitted hereunder. The distribution date elected by the
Participant for payment of fees deferred in a given year shall be the Scheduled
Withdrawal Date. A Participant's Scheduled Withdrawal Date with respect to
amounts deferred in a given year can be no earlier than two years from the last
day of the year in which the deferrals are made, other than for termination of
service, and will be no later than the date the Participant terminates service
as a Director. Payment may be made in one lump sum or equal annual installments
based on the number of Share Units attributable to the applicable Deferral
Election determined as of the September 30 immediately preceding commencement of
distribution. Installments may not be made more often than monthly and may not
extend for more than five years. The time of and method of distribution of
benefits may vary with each separate Deferral Election. The Deferral Accounts do
not represent rights to acquire the Company's Common Shares; payment may be made
in either the Company's Common Shares or cash at the sole discretion of the
Administrator. The Participant may change a Scheduled Withdrawal Date by
submitting a new Deferral Election Form at least thirteen (13) months prior to
the date the Participant otherwise


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would have received the distribution. The new Scheduled Withdrawal Date selected
by the Participant must be at least two (2) years following the date the new
Deferral Election Form is submitted. In the event a Participant does not elect a
Scheduled Withdrawal Date, all deferred amounts will be distributed upon
termination of service. The Administrator may elect to accelerate the payment of
any Deferral Account in its sole discretion.

         6. EARLY WITHDRAWAL ELECTION. A Participant may elect, at any time, to
withdraw all or a portion of his or her Deferral Account, calculated as if the
Participant had terminated service as of the day of the election, less an early
withdrawal penalty equal to 10% of such amount (the net amount shall be referred
to a the "Early Withdrawal Amount"). The Administrator will pay the Early
Withdrawal Amount as soon as possible after receiving the Participant's early
withdrawal election.

         7. DEATH OR DISABILITY.

            (A) In the event a Participant's service is terminated by reason of
death or disability prior to the distribution of any portion of that
Participant's Deferral Account, the Administrator will, within ninety (90) days
of the date of service termination, commence distribution of amounts credited to
the Deferral Account to the beneficiary or beneficiaries of the Participant or
to the Participant. Distribution will be made in accordance with the method of
distribution elected by the Participant or beneficiary pursuant to paragraph 5
hereof. In the event a Participant's death or disability occurs after
distribution of amounts credited to the Deferral Account hereunder has begun,
the Administrator will continue to make distributions to the Participant (or to
the beneficiary or beneficiaries in the event of death) in accordance with the
methods of distribution elected by the Participant pursuant to paragraph 5
hereof.


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            (B) Each Participant has the right to designate one or more
beneficiaries to receive distributions in the event of a Participant's death by
filing with the Administrator a Beneficiary Designation Form. The designated
beneficiary or beneficiaries may be changed by a Participant at any time prior
to that Participant's death by the delivery to the Administrator of a new
Beneficiary Designation Form. If no beneficiary has been designated, or if no
designated beneficiary survives the Participant, distributions pursuant to this
provision will be made to the Participant's estate.

         8. ASSIGNMENT AND ALIENATION OF BENEFITS. The right of each Participant
to any account, benefit or payment hereunder will not, to the extent permitted
by law, be subject in any manner to attachment or other legal process for the
debts of that Participant; and no account, benefit or payment will be subject to
anticipation, alienation, sale, transfer, assignment or encumbrance except by
will, by the laws of descent and distribution, or by a Participant election to
satisfy a property settlement agreement pursuant to a divorce.

         9. EFFECT OF CHANGE OF CONTROL. In the event of a Change of Control of
the Company, the entire unpaid balance of the Deferred Account shall be paid in
a lump sum to the Participant as of the effective date of the Change of Control.
Change of Control shall mean the first to occur of any of the following events:

            (A) any "person" as such term is used in Sections 13(d) and 14(d) of
the Securities Exchange Act of 1934 (the "1934 Act"), (other than (i) the
Company, (ii) any subsidiary of the Company, (iii) any trustee or other
fiduciary holding securities under an employee benefit plan of the Company or of
any subsidiary of the Company, or (iv) any company owned, directly or
indirectly, by the stockholders of the Company in substantially the same
proportions as their ownership of stock of the Company), is or becomes the
"beneficial



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owner" (as defined in Section 13(d) of the 1934 Act), together with all
Affiliates and Associates (as such terms are used in Rule 12b-2 of the General
Rules and Regulations under the 1934 Act) of such person, directly or
indirectly, of securities of the Company representing thirty percent (30%) or
more of the combined voting power of the Company's then outstanding securities;
or

            (B) the stockholders of the Company approve a merger or
consolidation of the Company with any other company, other than (i) a merger or
consolidation which would result in the voting securities of the Company
outstanding immediately prior thereto continuing to represent (either by
remaining outstanding or by being converted into voting securities of the
surviving entity), in combination with the ownership of any trustee or other
fiduciary holding securities under an employee benefit plan of the Company or
any subsidiary of the Company, at least sixty percent (60%) of the combined
voting power of the voting securities of the Company or such surviving entity
outstanding immediately after such merger or consolidation or (ii) a merger or
consolidation effected to implement a recapitalization of the Company (or
similar transaction) after which no "person" (with the method of determining
"beneficial ownership" used in clause (a) of this definition) owns more than
thirty percent (30%) of the combined voting power of the securities of the
Company or the surviving entity of such merger or consolidation; or

            (C) during any period of two (2) consecutive years (not including
any period prior to the execution of the Plan), individuals who at the beginning
of such period constitute the Board, and any new Director (other than a Director
designated by a person who has conducted or threatened a proxy contest, or has
entered into an agreement with the Company to effect a transaction described in
clause (a), (b) or (d) of this definition) whose election by the Board or
nomination for election by the Company's stockholders was approved by a vote of
at least



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two-thirds (2/3) of the Directors then still in office who either were Directors
at the beginning of the period or whose election or nomination for election was
previously so approved cease for any reason to constitute at least a majority
thereof; or

             (D) the stockholders of the Company approve a plan of complete
liquidation of the Company or an agreement for the sale or disposition by the
Company of all or substantially all of the Company's assets.

         10. UNSECURED OBLIGATION. The obligation of the Company to make
payments of amounts credited to the Participant's Deferred Account shall be a
general obligation of the Company, and such payment shall be made from general
assets and property of the Company. The Participant's relationship to the
Company under the Plan shall be only that of a general unsecured creditor and
neither this Plan, nor any agreement entered into hereunder, or action taken
pursuant hereto shall create or be construed to create a trust for purposes of
holding and investing the Deferred Account balances. The Company reserves the
right to establish such a trust, but such establishment shall not create any
rights in or against any amounts held thereunder.

         11. AMENDMENT OR TERMINATION. The Board of Directors of the Company may
amend or terminate this Plan at any time and from time to time. Any amendment or
termination of this Plan will not affect the rights of a Participant accrued
prior thereto without that Participant's written consent.

         12. TAXES. The Company is not responsible for the tax consequences
under federal, state or local law of any election made by any Participant under
the Plan. All payments under the Plan are subject to withholding and reporting
requirements to the extent required by applicable law.


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         13. NO RIGHT TO CONTINUED MEMBERSHIP ON THE BOARD. Nothing in this Plan
confers upon any director any right to continue as a director of the Company or
interferes with the rights of the Company and its shareholders, which are hereby
expressly reserved to remove any director at any time for any reason whatsoever,
with or without cause.

         14. APPLICABLE LAW. This Plan is governed under the laws of the State
of Illinois.



            IN WITNESS WHEREOF, the Company has caused this Plan to be executed
by its ____________________________________ this _______ day of ______________.


                                          CABOT MICROELECTRONICS CORPORATION



                                          By:
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