MATTSON TECHNOLOGY ANNOUNCES FILING OF FORM S-3 REGISTRATION STATEMENT REGARDING SHARES HELD BY STEAG ELECTRONIC SYSTEMS

FREMONT, Calif.- August 23, 2004 - Mattson Technology, Inc. (NASDAQ: MTSN), a leading supplier of advanced process equipment used to manufacture semiconductors, today announced that it has filed a Form S-3 shelf registration statement with the Securities and Exchange Commission. When effective, the registration statement will cover future sales of up to 8,861,144 shares of already outstanding Mattson common stock held by STEAG Electronic Systems AG of Essen, Germany, one of the Company’s principal stockholders. Of the total shares covered, 2,911,144 shares had been previously registered. The balance represents previously unregistered shares held by STEAG.

Mattson and STEAG previously announced STEAG’s intention to gradually reduce its ownership position in Mattson. The Company will receive no proceeds from any sale of stock by STEAG.

A registration statement relating to these securities has been filed with the Securities and Exchange Commission, but has not yet become effective. Those securities that have not been previously registered may not be sold nor may offers to buy be accepted prior to the time the registration statement becomes effective, except in transactions that are exempt from the registration requirements of applicable securities laws. This announcement shall not constitute an offer to sell or a solicitation of an offer to buy nor shall there be any sale of these securities in any State in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such State.

A written prospectus, when available, meeting the requirements of Section 10 of the Securities Act may be obtained from Investor Relations, Mattson Technology, Inc. 47131 Bayside Parkway, Fremont, CA 94538.

About Mattson Technology, Inc.

Mattson Technology, Inc. is a leading supplier of semiconductor wafer processing equipment used in the fabrication of integrated circuits. The company’s dry strip and RTP equipment utilize innovative technology to deliver advanced processing capabilities on high-productivity platforms for the fabrication of current- and next-generation devices. Since beginning operations in 1989, the company’s core vision has been to help bring technology leadership and productivity gains to semiconductor manufacturers worldwide. For more information, please contact Mattson Technology, Inc., 47131 Bayside Parkway, Fremont, Calif. 94538. Telephone: (800) MATTSON/(510) 657-5900. Fax: (510) 492-5911. Internet: www.mattson.com.