A MOSFET device including a semiconductor substrate, an SiGe layer provided on top of the semiconductor substrate, an Si layer provided on top of the SiGe layer; and a first isolation region for separating the Si layer into a first region and a second region, wherein the Si layer in the second region is turned into an Si epitaxial layer greater in thickness than the Si layer in the first region. The MOSFET device further includes at least one first MOSFET with the Si layer in the first region serving as a strained Si channel, and at least one second MOSFET with the Si epitaxial layer serving as an Si channel.