Silicon carbide semiconductor device and power converter

A silicon carbide semiconductor device comprising:

• a silicon carbide semiconductor substrate;
• a semiconductor layer formed on an upper surface of the silicon carbide semiconductor substrate;
• and
• a backside electrode formed on part of a lower surface of the silicon carbide semiconductor substrate,
• wherein a region in which a field-effect transistor is formed in a surface layer of the semiconductor layer and on an upper surface of the semiconductor layer is regarded as an active region,
• a region that surrounds the active region in plan view is regarded as a termination region,
• a region in which the backside electrode is formed in plan view is regarded as a first region,
• a region in which the backside electrode is not formed in plan view is regarded as a second region,
• the second region is a region that extends across a region boundary in plan view, the region boundary being a boundary between the active region and the termination region,
• a distance Di in plan view between the region boundary and an edge of the second region that is included in the active region in plan view satisfies T≤Di≤T×10, and
• a distance Do in plan view between the region boundary and an edge of the second region that is included in the termination region in plan view satisfies T≤Do,
• when T is a total thickness of the silicon carbide semiconductor substrate and the semiconductor layer.

A power converter, comprising:

• a conversion circuit that includes a silicon carbide semiconductor device and converts and outputs input electric power;
• a driving circuit that outputs a driving signal for driving the silicon carbide semiconductor device to the silicon carbide semiconductor device;
• and
• a control circuit that outputs a control signal for controlling the driving circuit to the driving circuit, wherein the silicon carbide semiconductor device includes:
• a silicon carbide semiconductor substrate of a first conductivity type;
• a semiconductor layer of the first conductivity type formed on an upper surface of the silicon carbide semiconductor substrate;
• and
• a backside electrode formed on a lower surface of the silicon carbide semiconductor substrate,
• wherein a region in which a field-effect transistor is formed in a surface layer of the semiconductor layer and on an upper surface of the semiconductor layer is regarded as an active region,
• a region that surrounds the active region in plan view is regarded as a termination region,
• a region in which electric resistivity between the silicon carbide semiconductor substrate and the backside electrode takes a first value is regarded as a first resistance region,
• a region in which the electric resistivity between the silicon carbide semiconductor substrate and the backside electrode takes a second value greater than the first value is regarded as a second resistance region,
• the second resistance region is a region that extends across a region boundary in plan view, the region boundary being a boundary between the active region and the termination region,
• a distance Di in plan view between the region boundary and an edge of the second resistance region that is included in the active region in plan view satisfies T≤Di≤T×10, and
• a distance Do between the region boundary and an edge of the second resistance region that is included in the termination region in plan view satisfies T≤Do,
• where T is a total thickness of the silicon carbide semiconductor substrate and the semiconductor layer.