A semiconductor device and its manufacture method wherein the semiconductor substrate has first and second insulating films, the first insulating film being an insulating film other than a silicon nitride film formed at least on a side wall of a conductive pattern including at least one layer of metal or metal silicide, and the second insulating film being a silicon nitride film formed to cover the first insulating film and the upper surface and side wall of the conductive pattern. The first insulating film may be formed to cover the upper surface and side wall of the conductive pattern. A semiconductor device and its manufacture method are provided which can realize high integrated DRAMs of 256 M or larger without degrading reliability and stability.