The semiconductor device fabrication method according the present invention having, forming an interlayer dielectric film containing carbon above a semiconductor substrate, forming a protective film on that portion of the interlayer dielectric film, which is close to the surface and in which the carbon concentration is low, forming a trench by selectively removing a desired region of the interlayer dielectric film and protective film, such that the region extends from the surface of the protective film to the bottom surface of the interlayer dielectric film, supplying carbon to the interface between the interlayer dielectric film and protective film, and forming a conductive layer by burying a conductive material in the trench.