Silicon carbide semiconductor device

A silicon carbide semiconductor device including an element region and a non-element region being provided outside the element region in plan view, the silicon carbide semiconductor device comprising:

• a silicon carbide semiconductor substrate extending across the element region and the non-element region;
• a drift layer being provided on the silicon carbide semiconductor substrate, being made of silicon carbide, and having a first conductivity type;
• a base region being disposed in the element region, being provided on the drift layer, and having a second conductivity type different from the first conductivity type;
• a source region being disposed in the element region, being provided on the base region,
• and having the first conductivity type;
• a first trench having a side surface penetrating the source region and the base region, and a bottom surface;
• a gate insulation film being provided on the side surface and on the bottom surface of the first trench;
• a gate electrode being provided in the first trench through the gate insulation film;
• a first relaxation region being disposed below the first trench, being in contact with the drift layer, and having the second conductivity type;
• a source pad electrode being electrically connected to the source region and the first relaxation region;
• a gate pad electrode being disposed in the non-element region, and being electrically connected to the gate electrode;
• at least one impurity region being disposed under the gate pad electrode in at least the non-element region, being provided on the drift layer under the gate pad electrode, having the first conductivity type, and having a higher impurity concentration of the first conductivity type than an impurity concentration of the first conductivity type of the drift layer;
• at least one second trench having a side surface penetrating the at least one impurity region, and a bottom surface;
• and
• at least one second relaxation region being disposed below the at least one second trench, being in contact with the drift layer, and having the second conductivity type, wherein
• in plan view, between the element region and the non-element region, the silicon carbide semiconductor device includes a contact region in which a part of the at least one impurity region is disposed and in which a third trench is provided, and in the contact region, the at least one impurity region and the source pad electrode are electrically connected, and
• the silicon carbide semiconductor device further comprises a third relaxation region being disposed below the third trench, being electrically connected to each of the source pad electrode and the at least one second relaxation region, and having the second conductivity type,
• wherein the element region is a region in which a cell that actually functions as a transistor is disposed, and the non-element region is a region in which the gate pad electrode for supplying the gate electrode with a desired voltage from outside is disposed.