Semiconductor device

A semiconductor device, comprising:

• a semiconductor substrate of a first conductivity type, formed of a silicon carbide semiconductor;
• an active region disposed on a front surface of the semiconductor substrate and through which main current flows, the active region having a periphery;
• and
• an edge termination structure surrounding a periphery of the active region, wherein
• the edge termination structure includes:
• a plurality of semiconductor regions disposed concentrically surrounding a periphery of the active region, the farther outward a semiconductor region thereamong is arranged, the lower an impurity concentration thereof is, and
• an intermediate region disposed so as to mutually contact adjacent ones of the plurality of semiconductor regions, the intermediate region having an impurity concentration that is lower than that of the adjacent semiconductor region on a side closer to the periphery of the active region and an impurity concentration that is higher than that of the adjacent semiconductor region on a side further from the active region,
• the intermediate region is divided into a plurality of sections concentrically surrounding the adjacent semiconductor region on a side closer to the periphery of the active region,
• a plurality of first subregions of the second conductivity type and a plurality of second subregions of the second conductivity type, the plurality of second subregions of the second conductivity type having an impurity concentration that is lower than that of the plurality of first subregions of the second conductivity type, alternately and repeatedly arranged, are disposed concentrically in the sections from an inner side toward an outer side relative to the periphery of the active region,
• each of the plurality of sections has an average impurity concentration determined based on widths of the plurality of first subregions and the plurality of second subregions arranged in the said section, where the average impurity concentration is lower the farther outward the said section is arranged relative to the periphery of the active region,
• an average impurity concentration difference between all adjacent sections is equal, and
• a microregion including adjacent ones of the plurality of first subregions and the plurality of second subregions has an average impurity concentration equal to the average impurity concentration of the section in which the microregion is arranged.

A semiconductor device, comprising:

• a semiconductor substrate of a first conductivity type, formed of a silicon carbide semiconductor;
• an active region disposed on a front surface of the semiconductor substrate and through which main current flows, the active region having a periphery;
• and
• an edge termination structure surrounding a periphery of the active region, wherein
• the edge termination structure includes:
• a plurality of semiconductor regions disposed concentrically surrounding a periphery of the active region, the farther outward a semiconductor region thereamong is arranged, the lower an impurity concentration thereof is, and
• an intermediate region disposed so as to mutually contact adjacent ones of the plurality of semiconductor regions, the intermediate region having an impurity concentration that is lower than that of the adjacent semiconductor region on a side closer to the periphery of the active region and an impurity concentration that is higher than that of the adjacent semiconductor region on a side further from the active region,
• the intermediate region is divided into a plurality of sections concentrically surrounding the adjacent semiconductor region on a side closer to the periphery of the active region,
• a plurality of first subregions of the second conductivity type and a plurality of second subregions of the second conductivity type, the plurality of second subregions of the second conductivity type having an impurity concentration that is lower than that of the plurality of first subregions of the second conductivity type, alternately and repeatedly arranged, are disposed concentrically in the sections from an inner side toward an outer side relative to the periphery of the active region,
• each of the plurality of sections has an average impurity concentration determined based on widths of the plurality of first subregions and the plurality of second subregions arranged in the said section, where the average impurity concentration is lower the farther outward the said section is arranged relative to the periphery of the active region,
• an average impurity concentration difference between all adjacent sections is equal, and
• the innermost section of the plurality of sections has an average impurity concentration that is 90 percent or more of the average impurity concentration of the semiconductor region adjacent on the inner side of the section relative to the periphery of the active region.