Patent ID: 8735982

Claim:
A semiconductor device comprising: a heavily doped semiconductor substrate of a first conductivity type; a first alternating-conductivity-type layer comprising a column-shaped or a layer-shaped first semiconductor region of the first conductivity type and a column-shaped or a layer-shaped second semiconductor region of a second conductivity type, the first and second semiconductor regions adjoining each other and repeating in parallel to a surface of the semiconductor substrate in order to form a pn-junction, wherein the pn-junctions extend perpendicularly to the surface of the semiconductor substrate and wherein the first alternating-conductivity-type layer is a drift layer that makes a current flow in an ON-state of the semiconductor device and sustains a voltage in an OFF-state of the semiconductor device; a surface structure on a surface side of the first alternating-conductivity-type layer, the surface structure constituting an active section that makes the current flow; an edge-termination section surrounding the active section; a second alternating-conductivity-type layer in the edge-termination section, the second alternating-conductivity-type layer comprising a column-shaped fourth semiconductor region of the second conductivity type in a third semiconductor region of the first conductivity type, the third and fourth semiconductor regions adjoining each other and repeating in parallel to the surface of the semiconductor substrate to form a pn-junction, wherein the pn-junctions extend perpendicularly to the surface of the semiconductor substrate; wherein a width of the fourth semiconductor region in the second alternating-conductivity-type layer becomes narrower at a predetermined rate from an edge on a side of the active section toward an edge of the edge termination section.