An improved migration resistance of the interconnect is provided and a diffusion of silicon into the inside of the interconnect is suppressed. A semiconductor device includes a silicon substrate, a first insulating film provided on the silicon substrate and composed of an SiCN film, an SiOC film and an SiO.sub.2 film, and a first copper interconnect provided in the first insulating film and essentially composed of a copper-containing metal. An Si--O unevenly distributed layer doped with injected silicon is included in the vicinity of the surface in the inside of the first copper interconnect, and injected atomic silicon at least partially creates Si--O bond.