Exhibit 10.www(12)

AMENDMENT NO. 3 TO THE REVOLVING CREDIT AGREEMENT

AMENDMENT NO. 3, dated as of March 11, 2003 (this ‘Amendment No. 3’) to the
Revolving Credit Agreement, dated as of December 21, 2001, among MEMC ELECTRONIC
MATERIALS, INC., a Delaware corporation (the ‘Borrower’), the Lenders party
thereto, and CITICORP USA, INC., as administrative agent and collateral agent,
as amended by Amendment No. 1 to the Revolving Credit Agreement, dated March 21,
2002, among the parties therein, and Amendment No. 2 to the Revolving Credit
Agreement, dated June 21, 2002, among the parties therein (as amended, modified
or supplemented from time to time, the ‘Revolving Credit Agreement’).

W I T N E S S E T H :

WHEREAS, pursuant to Section 9.02 of the Revolving Credit Agreement, the
Borrower and the Required Lenders wish to amend the Revolving Credit Agreement
as set forth herein;

NOW THEREFORE, in consideration of the premises herein, and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the parties
hereto hereby agree as follows:

1. Definitions. Capitalized terms used herein and not defined herein have the
meanings assigned to them in the Revolving Credit Agreement.

2. Amendments to the Revolving Credit Agreement. (a) The definitions of
‘Investor Revolving Credit Agreement’ and 'Investor Guarantee Agreement' are
hereby added in Section 1.01 as follows:

‘Investor Revolving Credit Agreement’ has the meaning assigned to such term in
the Security Agreement, as amended.

‘Investor Guarantee Agreement’ means the guarantee agreement, dated as of March
3, 2003, among the Subsidiary Loan Parties (as defined in the Investor Revolving
Credit Agreement) and the Collateral Agent (as defined in the Investor Revolving
Credit Agreement) for the benefit of the secured parties under the Investor
Revolving Credit Agreement, as such agreement may be further amended,
supplemented or modified.

(b) Section 6.11 is hereby amended to insert the following text immediately
after the words ‘Indenture Documentation,’: ‘Article X of the Investor Revolving
Credit Agreement, Article 2 of the Investor Guarantee Agreement,’.

3. Effective Date. This Amendment No. 3 shall become effective as of the date
first written above (the ‘Third Amendment Effective Date’).

4. Reference to and Effect on the Revolving Credit Agreement.

(a) On and after the Third Amendment Effective Date, each reference in the
Revolving Credit Agreement to 'this Agreement', 'hereunder', 'hereof', 'herein'
or words of like import referring to the Revolving Credit Agreement, shall mean
and be a reference to the Revolving Credit Agreement as amended by this
Amendment No. 3.

(b) Except as specifically amended by this Amendment No. 3, the Revolving Credit
Agreement shall remain in full force and effect and is hereby in all respects
ratified and confirmed.

(c) The execution, delivery and performance of this Amendment No. 3 shall not,
except as expressly

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provided herein, constitute a waiver or amendment of any provision of, or
operate as a waiver or amendment of any right, power or remedy of the Lenders
under the Revolving Credit Agreement.

5. GOVERNING LAW. THIS AGREEMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES
HEREUNDER SHALL BE CONSTRUED IN ACCORDANCE WITH AND BE GOVERNED BY THE LAW OF
THE STATE OF NEW YORK.

6. Counterparts. This Amendment No. 3 may be executed in any number of
counterparts, each of which when so executed shall be deemed to be an original
and all of which taken together shall constitute one and the same instrument.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 3 to be
executed by their respective officers thereunto duly authorized, as of the date
first above written.

MEMC ELECTRONIC MATERIALS, INC.

By: /s/ James M. Stolze
Name: James M. Stolze
Title: Executive Vice President, Chief Financial Officer

By: /s/ Kenneth L. Young
Name: Kenneth L. Young
Title: Treasurer

CITICORP USA, INC., as Lender By: /s/ Allen Fisher
Name: Allen Fisher
Title: UBS AG, STAMFORD BRANCH, as Lender By: /s/ Wilfred V. Saint
Name: Wilfred V. Saint
Title: Associate Director,
Banking Products Services, US By: /s/ Susan Bruhner
Name: Susan Bruhner
Title: Associate Director,
Banking Products Services, US CONSENTED TO AND AGREED:

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Name of Institution:

TPG PARTNERS III, L.P.

By: TPG GenPar III, L.P.,
Its General Partner

By: TPG Advisors III, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President

Name of Institution:

TPG PARALLEL III, L.P.

By: TPG GenPar III, L.P.,
Its General Partner

By: TPG Advisors III, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President Name of Institution:

TPG INVESTORS III, L.P.

By: TPG GenPar III, L.P.,
Its General Partner

By: TPG Advisors III, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President

Name of Institution:

FOF PARTNERS III, L.P.

By: TPG GenPar III, L.P.,
Its General Partner

By: TPG Advisors III, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President

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Name of Institution:

FOF PARTNERS III-B, L.P.

By: TPG GenPar III, L.P.,
Its General Partner

By: TPG Advisors III, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President

Name of Institution:

TPG DUTCH PARALLEL III, C.V.

By: TPG GenPar Dutch, L.L.C.,
Its General Partner

By: TPG GenPar III, L.P.,
Its Sole Member

By: TPG Advisors III, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President Name of Institution:

T3 PARTNERS, L.P.

By: T3 GenPar, L.P.,
Its General Partner

By: T3 Advisors, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President Name of Institution: T3 PARALLEL, L.P.

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By: T3 GenPar, L.P.,
Its General Partner

By: T3 Advisors, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President

Name of Institution:

T3 INVESTORS, L.P.

By: T3GenPar, L.P.,
Its General Partner

By: T3Advisors, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President Name of Institution:

T3 DUTCH PARALLEL, C.V.

By: T3GenPar Dutch, L.L.C.,
Its General Partner

By: T3GenPar, L.P.,
Its Sole Member

By: T3 Advisors, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President Name of Institution: T3 PARTNERS II, L.P.

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By: T3GenPar II, L.P.,
Its General Partner

By: T3Advisors II, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President

Name of Institution:

T3 PARALLEL II, L.P.

By: T3GenPar II, L.P.,
Its General Partner

By: T3Advisors II, Inc.,
Its General Partner

By: /s/ Richard A. Ekleberry
Name: Richard A. Ekleberry
Title: Vice President

CONSENTED TO AND AGREED:

Name of Institution: GREEN EQUITY INVESTORS III, L.P.
By: GEI Capital III, LLC, as its General Partner

By: /s/ John Danhakl
Name: John Danhakl
Title: Name of Institution: GREEN EQUITY INVESTORS III, L.P.
By: GEI Capital III, LLC, as its General Partner

By: /s/ John Danhakl
Name: John Danhakl
Title:

CONSENTED TO AND AGREED:

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Name of Institution: TCW/CRESCENT MEZZANINE PARTNERS III, L.P.,
TCW/CRESCENT MEZZANINE TRUST III and
TCW/CRESCENT MEZZANINE PARTNERS III NETHERLANDS, L.P.

By: TCW/Crescent Mezzanine Management III, L.L.C.,
as Its Investment Manager

By: TCW Asset Management Company, as Its Sub- Advisor

By: /s/ Jean-Marc Chapus
Name: Jean-Marc Chapus
Title: Group Managing Director

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