Semiconductor device having MOS transistor

摘要

A semiconductor device which can effectively prevent impurity diffusion in heat treatment for electrically activating the impurity, and a manufacturing method thereof are disclosed. In the semiconductor device, a diffusion preventing layer having a depth equal to or greater than a junction depth of source/drain regions is formed along the entire junction region of the source/drain regions. The diffusion preventing layer is formed near the surface at the side of a gate insulation layer of the gate electrode including impurity.