A wide band gap semiconductor device comprising: a drain electrode; a drift layer being a first conductivity type and provided above the drain electrode; a well region being a second conductivity type and provided in the drift layer; a source region being the first conductivity type and provided in the well region and electrically connected to a source pad; a gate electrode electrically connected to a gate pad; a gate contact region being the first conductivity type and provided in the well region and electrically connected to the gate pad; a Zener diode region provided in the well region and provided between the source region and the gate contact region in a plane direction; an interlayer insulating film; and a gate insulating film provided on the well region and provided between the well region and the interlayer insulating film, wherein the gate electrode is provided on the gate insulating film, characterized in that the Zener diode region has a superhigh-concentration second conductivity type semiconductor region electrically connected to the source pad and a high-concentration first conductivity type semiconductor region adjacent to the superhigh-concentration second conductivity type semiconductor region, the gate contact region is adjacent to the high-concentration first conductivity type semiconductor region, and the superhigh-concentration second conductivity type semiconductor region is provided at a side of the source region closer than the high-concentration first conductivity type semiconductor region; wherein the high-concentration first conductivity type semiconductor region has an impurity concentration of 1 × 10 18 to 2 × 10 19 cm -3, and wherein the superhigh-concentration second conductivity type semiconductor region has a higher impurity concentration of 2 × 10 19 to 1 × 10 21 cm -3. a drain electrode; a drift layer being a first conductivity type and provided above the drain electrode; a well region being a second conductivity type and provided in the drift layer; a source region being the first conductivity type and provided in the well region and electrically connected to a source pad; a gate electrode electrically connected to a gate pad; a gate contact region being the first conductivity type and provided in the well region and electrically connected to the gate pad; a Zener diode region provided in the well region and provided between the source region and the gate contact region in a plane direction; an interlayer insulating film; and a gate insulating film provided on the well region and provided between the well region and the interlayer insulating film, wherein the gate electrode is provided on the gate insulating film, characterized in that the Zener diode region has a superhigh-concentration second conductivity type semiconductor region electrically connected to the source pad and a high-concentration first conductivity type semiconductor region adjacent to the superhigh-concentration second conductivity type semiconductor region, the gate contact region is adjacent to the high-concentration first conductivity type semiconductor region, and the superhigh-concentration second conductivity type semiconductor region is provided at a side of the source region closer than the high-concentration first conductivity type semiconductor region; wherein the high-concentration first conductivity type semiconductor region has an impurity concentration of 1 × 10 18 to 2 × 10 19 cm -3, and wherein the superhigh-concentration second conductivity type semiconductor region has a higher impurity concentration of 2 × 10 19 to 1 × 10 21 cm -3.