Patent ID: 7745276

Claim:
A method for manufacturing a silicon carbide semiconductor device comprising: preparing a substrate made of silicon carbide having a (11-20)-orientation surface as a principal surface; forming a drift layer having a first conductivity type on the substrate; forming a base region having a second conductivity type in a surface portion of the drift layer by doping a second conductivity type impurity; forming a first conductivity type region in the base region in such a manner that the first conductivity type region has an impurity concentration higher than that of the drift layer; forming a channel region having the first conductivity type on a surface of the base region to couple between the drift layer and the first conductivity type region; forming a gate insulating film on a surface of the channel region; forming a gate electrode on the gate insulating film; forming a first electrode to electrically connect to the first conductivity type region; and forming a second electrode on a backside of the substrate, wherein the device is configured to control current between the first electrode and the second electrode through the first conductivity type region and the drift layer by controlling a channel formed in the channel region with an applied voltage to the gate electrode, wherein the forming the base region includes forming a lower part of the base region on the drift layer by an epitaxial growth method, the lower part contacting the drift layer, wherein the forming the base region further includes forming an upper part of the base region on the lower part, and wherein the forming the upper part includes: forming a first conductivity type layer on the drift layer; implanting a second conductivity type impurity having the second conductivity type into a part of the first conductivity type layer; and performing activation heat treatment for diffusing the second conductivity type impurity toward a <11-20> direction in the part of the first conductivity type layer, the forming the lower part of the base region includes: epitaxially growing a second conductivity type layer on a surface of the drift layer; forming a mask having an opening on the second conductivity type layer, wherein the opening corresponds to a base-region-to-be-formed region of the second conductivity type layer; and etching the second conductivity-type layer with using the mask to partly expose the drift layer and to form the lower part of the base region, the forming the first conductivity type region includes epitaxially growing the first conductivity type layer on the lower part of the base region and the drift layer, and the implanting the second conductivity type impurity into the part of the first conductivity type layer includes implanting the second conductivity type impurity into a base-region-to-be-formed region of the first conductivity type layer.