Silicon carbide MOS semiconductor device

A silicon carbide MOS semiconductor device comprising:

• a silicon carbide semiconductor substrate;
• a voltage blocking layer of a first conductivity type on a principal plane of the substrate;
• a body region of a second conductivity type on the voltage blocking layer:
• a body contact region in a surface region of the body region, the body contact region having impurity ions implanted therein and being of the second conductivity;
• a source contact region in a surface region of the body region, the source contact region having impurity ions implanted therein and being of the first conductivity type, the source contact region having an impurity concentration of 3×1019 cm−or higher and a thickness of from 0.3 μm to 0.4 μm, and having a tail part in a bottom region of the source contact region with a depth deeper than the depth of ion implantation in the source contact region;
• an electrode contacting the body contact region and the source contact region, wherein the surface impurity concentration of the body contact region and that of the source contact region are sufficient to cause an ohmic contact with the electrode;
• a source extension region under the source contact region at a region deeper than the tail part of the doping in the bottom region of the source contact region, the source extension region having impurity ions implanted therein with an impurity concentration of less than 3×1019 cm−, which concentration is lower than that in the source contact region and a depth of the source extension region being within 1 μm from the surface of the source contact region, and being formed under the tail part by selective ion implantation;
• and
• a trench formed from a top surface of the source contact region and passing through the source contact region, the source extension region, and the body region, and a gate electrode embedded in the trench on an internal surface thereof via an insulation film, an upper end of the embedded gate electrode being above the lower end of the source contact region,
• wherein the source contact region and the voltage blocking layer are separated from each other by the body region.