A semiconductor device includes a gate insulating film formed on a semiconductor region of a first conductivity type; a gate electrode formed on the gate insulating film; an offset spacer formed on a side surface of the gate electrode; an inner sidewall formed on the side surface of the gate electrode with the offset spacer interposed therebetween, and having an L-shaped cross section; and an insulating film formed to cover the gate electrode, the offset spacer, the inner sidewall, and a part of the semiconductor region located laterally outward from the inner sidewall. The offset spacer includes an inner offset spacer formed on the side surface of the gate electrode and an outer offset spacer formed to cover the side surface of the gate electrode and the inner offset spacer. The outer offset spacer is in contact with a top end and outer side surface of the inner offset spacer.