Abstract: A semiconductor device is constructed so that an insulation film is provided in regions other than a protruding portion of a substrate. A polycrystalline silicon layer and a metal silicide layer are formed over said insulation film to provide a multi-layer structure, and a take-out portion for at least one of the emitter, base, and collector members of a bipolar transistor provided in the mesa region is constituted by a film of this multi-layer structure. By virtue of the use of metal silicide together with the polycrystalline silicon, a very low resistance is achieved which enhances the device's operating speed. Further, the metal silicide is separated from the protruding portion of the substrate by a portion of the polycrystalline silicon to provide a smooth interface with the substrate. This smooth interface significantly reduces crystal defects in the single crystal substrate.