Taipei, Taiwan, R.O.C. – May 21, 2004 - United Microelectronics Corporation (TAIEX: 2303, NYSE: UMC), a world leading semiconductor foundry, today announced that it has decided to purchase 90 million UMCi shares from UMC Japan (UMCJ). The total cost of the purchase is US$117 million. After this transaction, UMC will own 95.23% of UMCi, an increase from the current level of 84.96%

As semiconductor demand remains strong, this investment will enhance UMC's control of UMCi's capacity allocation. UMCi is currently in full-scale production, and is focused on manufacturing products based on UMC's 0.13um and below technologies. UMCi has been extremely successful in leveraging its parent company's extensive 300mm experience. This knowledge and experience is currently being applied to its rapid production ramp-up, along with the implementation of single wafer processing to reduce lot size and cycle time. Production volume for the state-of-the-art 300mm automated facility is expected to reach 10,000 wafers by the end of 2004.

UMCi is located on a 12-hectare (30 acres) site in Singapore's Pasir Ris Wafer Park. Singapore is a rapidly emerging global IC manufacturing hub, and its well-established infrastructure and friendly government policies have attracted investment from the world's leading semiconductor companies.

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 UMCi are both in volume production for a variety of customer products. UMC employs over 9,000 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.