An extension region is formed by ion implantation under masking by a gate electrode, and then a substance having a diffusion suppressive function over an impurity contained in a source-and-drain is implanted under masking by the gate electrode and a first sidewall spacer so as to form amorphous layers a semiconductor substrate within a surficial layer thereof and in alignment with the first sidewall spacer, to thereby form an amorphous diffusion suppressive region.