Contract chipmakers Taiwan Semiconductor Manufacturing Company (TSMC) and United Microelectronics Corporation (UMC) both saw their September 2011 revenues decrease from those of the prior month and a year earlier.

TSMC generated NT$33.41 billion (US$1.1 billion) in September consolidated revenues, down 11.3% sequentially and 11.2% over September 2010.

UMC saw a narrower sequential drop but a bigger on-year decline in revenues. It reported NT$8.18 billion for September 2011, down 0.3% on month and 25.3% from a year ago.

TSMC's consolidated revenues for the July-September period reached NT$106.48 billion, topping the company's targeted NT$102-104 billion.

UMC's revenues for the third quarter of 2011 amounted to NT$25.19 billion, down about 10.5% from the NT$28.15 billion posted in the prior quarter. It previously estimated third-quarter revenues would slip by a larger 11-13% on quarter.

UMC is scheduled to hold its quarterly investors meeting on October 26 followed by TSMC's on October 27.