A semiconductor device includes: an isolation region formed in a semiconductor substrate; an active region surrounded by the isolation region in the semiconductor substrate; a gate insulating film formed on the active region; and a gate electrode formed across the boundary between the active region and the isolation region adjacent to the active region. The gate electrode includes a first portion which is located above the active region with the gate insulating film interposed therebetween and is entirely made of a silicide in a thickness direction and a second portion which is located above the isolation region and is made of a silicon region and the silicide region covering the silicon region.