A semiconductor device includes: a first active region surrounded with an isolation region of a semiconductor substrate; a first gate electrode formed over the first active region and having a protrusion protruding on the isolation region; a first side-wall insulating film; an auxiliary pattern formed to be spaced apart in the gate width direction from the protrusion of the first gate electrode; a second side-wall insulating film; and a stress-containing insulating film containing internal stress and formed to cover the first gate electrode, the first side-wall insulating film, the auxiliary pattern, and the second side-wall insulating film. In this device, the distance between the first gate electrode and the auxiliary pattern is smaller than the sum total of: the sum of the thicknesses of the first and second side-wall insulating films; and the double of the thickness of the stress-containing insulating film.