Patent ID: 7173284

Claim:
A silicon carbide semiconductor device that includes J-FETS, the device comprising: a semiconductor substrate that includes a substrate of a first conductivity type, which comprises silicon carbide and a drift layer of the first conductivity type, wherein the drift layer is comprised of epitaxially grown silicon carbide having a lower impurity concentration level than the substrate of the first conductivity type, wherein the drift layer is located on the substrate of the first conductivity type; a drain electrode formed on a backside of the substrate; a cell area, which is an area of the semiconductor substrate where the J-FETs are formed; and a peripheral area around the cell area, wherein the cell area comprises: trenches formed at the surface of the drift layer; first gate areas of a second conductivity type formed on inner walls of the trenches; a second gate area of the second conductivity type, wherein the second gate area has almost the same depth as the trenches and is formed in isolation from the trenches at the surface of the drift layer and in isolation from the first gate areas; a source area of the first conductivity type formed only in the cell area, wherein the source area has a higher impurity concentration level than the drift layer and is located on top of channel areas, wherein the channel areas are located between the first and second gate areas in the drift layer; a source electrode formed only in the cell area, wherein the source electrode is electrically connected to the source area; and the peripheral area comprises: trenches first gate areas; second gate area; first gate electrodes formed only in the peripheral area and electrically connected to the first gate areas; and a second gate electrode formed only in the peripheral area and electrically connected to the second gate area, wherein the device has a normally-off state in which substantially no current flows in the channel areas when substantially no voltage bias is applied to the first and second gate electrodes.