The present invention provides a semiconductor device and a method for manufacturing the same. The method includes: providing a substrate; forming a gate stack on the substrate; forming an inter layer dielectric (ILD) to cover the device; etching the ILD at both sides of the gate stack and the substrate below the ILD, so as to form a groove of source and drain regions respectively; depositing a metal diffusion barrier layer in the groove; and filling the groove with a metal to form the source and drain regions. The semiconductor device includes: a substrate; a gate stack on the substrate; an inter layer dielectric (ILD) covering the device; a groove of source and drain regions formed in the ILD at both sides of the gate stack and the substrate below the ILD; and a metal diffusion barrier layer and a metal filler formed in the groove. According to the present invention, the S/D parasitic resistance in the MOS device is reduced, the S/D stress on the channel is increased, the process temperature is lowered, and the process compatibility between the high k gate dielectric layer and the metal gate is improved.