Abstract: A semiconductor device having a groove provided in a semiconductor substrate, a gate insulating film provided so as to cover an inside surface of the groove, a first conductive film provided inside the groove in a position in which a first upper end surface is lower than the outer surface of the semiconductor substrate, a second conductive film provided inside the groove in a position that protrudes beyond the first upper end surface and in which a second upper end surface is higher than the outer surface of the semiconductor substrate, and a cap insulating film provided inside the groove so as to cover a protruding part of the second conductive film that protrudes beyond the first upper end surface.

Abstract: In a first method for manufacturing a semiconductor device, an opening is formed in a substrate. A tungsten film is formed on the substrate so as to fill up inside the opening, and then the tungsten film is annealed. The tungsten film is etched back so that the tungsten film remains inside the opening. In a second method for manufacturing a semiconductor device, a laminate body comprising a tungsten film and an insulating film on the tungsten film is formed on a substrate. The laminate body is annealed, and then the laminate body is etched back.