Patent ID: 7772704

Claim:
A semiconductor device comprising: a semiconductor substrate comprising a first surface and a second surface; a discrete semiconductor element formed in the semiconductor substrate; a first electrode and a second electrode that are disposed on the first surface and connected with the discrete semiconductor element; a first metal layer formed on the second surface so as to form an uppermost layer covering the second surface; and a second metal layer disposed between the first metal layer and the second surface of the semiconductor substrate, wherein the semiconductor device comprises a current path configured so that a current flows from the first electrode to first and second metal layers through the semiconductor substrate, flows along the first and second metal layers, and flows from the first and second metal layers to the second electrode through the semiconductor substrate upon application of voltages to the first and second electrodes, the first metal layer is thicker than the second metal layer, and the first metal layer has a higher degree of corrosion resistance or oxidation resistance than the second metal layer.