Patent ID: 7470930

Claim:
A silicon carbide semiconductor device including a semiconductor element, wherein the semiconductor element is disposed in a semiconductor substrate having a first conductive type silicon carbide layer and a silicon substrate, and wherein the first conductive type silicon carbide layer is disposed on a principal surface of the silicon substrate, the device comprising: a trench disposed on a surface of the silicon carbide layer to reach the silicon substrate; and a conductive layer disposed in the trench at a boundary portion between the silicon carbide layer and the silicon substrate to connect to both of the silicon carbide layer and the silicon substrate, wherein the semiconductor element is a vertical type semiconductor element so that current flows on both of a top surface portion and a backside surface portion of the semiconductor substrate, the current flows through the conductive layer, and a low resistance layer disposed at a boundary portion between the silicon carbide layer and the silicon substrate in such a manner that an impurity concentration of a first conductive type impurity in the low resistance layer is higher than that of the silicon carbide layer, the trench penetrates the low resistance layer and reaches the silicon substrate, the conductive layer is disposed in the trench to connect between the low resistance layer and the silicon substrate, the low resistance layer is made of silicon carbide, the low resistance layer and the silicon carbide layer are epitaxially disposed on the silicon substrate so that the low resistance layer, the silicon carbide layer and the silicon substrate provide a heteroepitaxial structure, the current flows from the top surface portion to the backside surface portion through the silicon carbide layer, the low resistance layer, the conductive layer and the silicon substrate, and the silicon carbide layer provides a drift layer, and the low resistance layer provides a drain.