A configuration for a substrate for a semiconductor device which makes it possible to achieve further stabilization of the voltage for driving a semiconductor element (5) to be mounted is provided. The substrate for a semiconductor device is provided with a base (1) and an electrically insulating film (3) formed on at least a portion of the surface of this base (1). The base (1) is made of one type of material selected from the group consisting of an alloy including copper and tungsten, an alloy including copper and molybdenum, an alloy including copper, tungsten and molybdenum, a composite material including aluminum and silicon carbide, and a composite material including silicon and silicon carbide. The electrically insulating film (3) includes plural layers made of at least one type of film selected from the group consisting of a diamond-like carbon film, an aluminum oxide film and a silicon oxide film.