UMC Announces Convertible Bond Pricing

Taipei, Taiwan, R.O.C. - September 29, 2005 - United Microelectronics Corporation (TAIEX: 2303, NYSE: UMC) today announced the pricing of its private offering of US$381.4 million aggregate principal amount of Convertible Bonds due 2008. The sale of the bonds is expected to close on October 5, 2005.

The bonds are redeemable at maturity at a price of 100% of their principal amount, equivalent to a yield to maturity of 0% per annum. The bonds are convertible into UMC American Depositary Shares at an initial conversion price of $3.814 per American Depositary Share, subject to adjustment in certain circumstances. On September 27, 2005, the reported closing price per American Depositary Share of UMC on the New York Stock Exchange was $3.26. Application has been made to list the bonds on the EuroMTF Market of the Luxembourg Stock Exchange.

UMC intends to use the net proceeds to fund purchases of raw materials abroad.

The bonds will be offered outside the United States pursuant to Regulation S under the United States Securities Act of 1933, as amended. The bonds and the American Depositary Shares into which the bonds are convertible have not been, and will not be, registered by UMC under the Securities Act and will not be offered or sold in the United States.

About UMC
UMC (NYSE: UMC, TSE: 2303) is a leading global semiconductor foundry that manufactures advanced process ICs for applications spanning every major sector of the semiconductor industry. UMC delivers cutting-edge foundry technologies that enable sophisticated system-on-chip (SoC) designs, including 90nm copper, 0.13um copper, and mixed signal/RFCMOS. UMC is also a leader in 300mm manufacturing; Fab 12A in Taiwan and Singapore-based Fab 12i are both in volume production for a variety of customer products. UMC employs approximately 10,500 people worldwide and has offices in Taiwan, Japan, Singapore, Europe, and the United States. UMC can be found on the web at http://www.umc.com.

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