Taiwan-based United Microelectronics, the world's second- largest foundry in terms of market share, went public as an American depositary receipt in the United States in 2000. The firm manufactures semiconductors for chipmakers such as AMD and Xilinx. However, the company has consistently lagged Taiwan Semiconductor in terms of market share and operating efficiency. UMC also holds several types of investments in other tech firms, which have provided it with incremental income in recent years.