UMC Announces Capital Reduction
from the Retirement of 1 Billion Treasury Shares

Taipei, Taiwan, R.O.C. – June 5, 2006 - United Microelectronics Corporation (TAIEX: 2303, NYSE: UMC), today received approval from the relevant government authorities for the completion of its capital amendment registration, effective from June 2, to retire 1 billion treasury shares. The paid-in capital has thus been reduced to NT$188,452,340,740 from NT$198,452,340,740.

UMC announced its 10th share buy-back program on February 15, 2006, to repurchase 1 billion shares, or 5.04% of the total issued shares, from the open market. The shares were then to be retired for the purpose of raising shareholders’ equity. UMC completed the 1 billion shares buy-back program on April 11, 2006, with an average buy-back price of NT$19.65 per share. UMC cancelled the 1 billion shares as planned and completed the capital reduction registration on June 2, 2006.

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 volume production 90nm, industry-leading 65nm, and mixed signal/RFCMOS. UMC’s 10 wafer manufacturing facilities include two advanced 300mm fabs; Fab 12A in Taiwan and Singapore-based Fab 12i are both in volume production for a variety of customer products. The company employs approximately 12,000 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