Patent ID: 7423315

Claim:
A semiconductor device comprising: a first-conductivity type semiconductor substrate; a pillar structure portion formed on the first-conductivity type semiconductor substrate and formed of five semiconductor pillar layers arranged in one direction parallel to a main surface of the first-conductivity type semiconductor substrate; and isolation insulating portions formed on the first-conductivity type semiconductor substrate and sandwiching the pillar structure portion between the isolation insulating portions, wherein the pillar structure portion is formed of a first first-conductivity type pillar layer, a second first-conductivity type pillar layer and a third first-conductivity type pillar layer which sandwich the first first-conductivity type pillar layer, a first second-conductivity type pillar layer provided between the first first-conductivity type pillar layer and the second first-conductivity type pillar layer, and a second second-conductivity type pillar layer provided between the first first-conductivity type pillar layer and the third first-conductivity type pillar layer, wherein the second first-conductivity type pillar layer has a first-conductivity type impurity concentration higher than that of the first first-conductivity type pillar layer and that of the first second-conductivity type pillar layer, and the third first-conductivity type pillar layer has a first-conductivity type impurity concentration higher than that of the first-conductivity type pillar layer and that of the second second-conductivity type pillar layer, the second first-conductivity type pillar layer has a second-conductivity type impurity concentration higher than that of the first first-conductivity type pillar layer and that of the first second-conductivity type pillar layer, and the third first-conductivity type pillar layer has a second-conductivity type impurity concentration higher than that of the first-conductivity type pillar layer and that of the second-second-conductivity type pillar layer, and each of the first second-conductivity type pillar layer and the second-conductivity type pillar layer has a second-conductivity type impurity concentration higher than that of the first first-conductivity type pillar layer.