The present invention discloses a semiconductor device, which comprises a substrate, a gate stack structure on the substrate, a channel region in the substrate under the gate stack structure, and source and drain regions at both sides of the channel region, wherein there is a stressed layer under and at both sides of the channel region, in which the source and drain regions are formed. According to the semiconductor device and the method for manufacturing the same of the present invention, a stressed layer is formed at both sides of and under the channel region made of a silicon-based material so as to act on the channel region, thereby effectively increasing the carrier mobility of the channel region and improving the device performance.