US Patent 7485517 Fabricating method of semiconductor device

A method for fabricating a semiconductor device is provided. First, a substrate is provided, and a first-type MOS (metallic oxide semiconductor) transistor, an input/output (I/O) second-type MOS transistor, and a core second-type MOS transistor are formed on the substrate. Then, a first stress layer is formed to overlay the substrate, the first-type MOS transistor, the I/O second-type MOS transistor, and the core second-type MOS transistor. Then, at least the first stress layer on the core second-type MOS transistor is removed to reserve at least the first stress layer on the first-type MOS transistor. Finally, a second stress layer is formed on the core second-type MOS transistor.