A semiconductor device and a method for manufacturing the same is disclosed, in which a spacer containing nitrogen therein has a tensile stress and enables device reliability improvement by improving the On-current without regard to the kind of transistor. The semiconductor device includes a semiconductor substrate; a gate insulating layer and a gate electrode on the semiconductor substrate; spacers at sidewalls of the gate electrode, wherein the spacer contains nitrogen to obtain or increase its tensile stress; and source and drain regions in the semiconductor substrate adjacent to the gate electrode.