A semiconductor device comprises a semiconductor substrate in which a semiconductor element is formed, an interlayer insulating film formed on the semiconductor substrate, an insulating barrier layer, formed on the interlayer insulating film by plasma nitriding, for preventing diffusion of a metal constituting a wiring layer, a conductive barrier layer, formed on the insulating barrier layer, for preventing diffusion of the metal, and a wiring layer formed of the metal on the conductive barrier layer. A bottom portion of the wiring layer is protected by the conductive barrier layer and the insulating barrier layer. Therefore, the diffusion of the metal constituting the wiring layer can be surely prevented.