A semiconductor device includes a side wall spacer formed on the side surface of a gate electrode formed on the upper side of a semiconductor substrate with a gate insulation film therebetween, extension regions built up on the semiconductor substrate, and source/drain regions formed on the extension regions, wherein a first epitaxial layer is formed so as to fill up portions, cut out at the time of forming the side wall spacer, of the semiconductor substrate, and the extension regions are formed on the first epitaxial layer from a second epitaxial layer of a conduction type opposite to that of the first epitaxial layer.