UMC Announces Share Buy-Back Program

Taipei, Taiwan, R.O.C. – September 29, 2005 - United Microelectronics Corporation (TAIEX: 2303, NYSE: UMC), today held a meeting of the Board of Directors and Supervisors, at which the Board passed a resolution to repurchase 250 million shares from the open market. This is the ninth stock buy-back program announced by the company. The details for the share buy-back program are as follows:

1. Purpose of the share buy back: Transfer to employees
2. Planned buy-back period: Between September 30, 2005 and November 29, 2005.
3. Number of shares: 250,000,000 shares
4. Target price range for buyback: NT$14.00 to NT$30.65. If the market price falls below the lowest range, the company is still authorized to purchase the shares.
5. The shares will be purchased from the open market.
6. The number of shares to be bought back is 1.27% of the total issued shares of the company.
7. The company currently holds 692,067,000 shares of its stock from the previous eight stock buy-back programs.

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.