A semiconductor device includes a PMOS transistor of a peripheral circuit region. The PMOS transistor is formed over a silicon germanium layer to have a compressive strain structure, thereby increasing hole mobility of a channel region in operation of the device. The semiconductor device may include a second active region including a silicon layer connected to a first active region of a semiconductor substrate, a silicon germanium layer formed over the silicon layer expected to be a PMOS region, and a PMOS gate formed over the silicon germanium layer.