Abstract: A plurality of trenches are formed in a semiconductor substrate, and an insulating film is formed over the plurality of trenches and the semiconductor substrate. A resist layer is then formed over the insulating film. The resist layer is then patterned such that remaining portions of the resist layer extend over first trenches of at least a given width and such that removed portions of the resist layer extend over second trenches of less then the given width. The insulating film is then etched using the remaining portions of the resist layer as a mask to expose the second trenches. The remaining portions of the resist layer are then removed to expose portions of the insulating film protruding above the first trenches. The exposed portions of the insulating film protruding above the first trenches is then chemical mechanical polished.

Abstract: A dummy active region is formed in which abrading processes are averaged. A semiconductor device is characterized in that an active region for forming an actual device, a device separation region being formed by a trench, and a dummy active region formed substantially in a rectangular shape are included, and the length of the short side of the dummy active region is less than 1 &mgr;m.

Abstract: An object of the present invention is to improve a margin for the formation of a trench device separation region at photolitho.