Patent ID: 8531007

Claim:
A semiconductor device comprising: an active section in a semiconductor substrate of a first conductivity type; an edge termination section in the semiconductor substrate, the edge termination section having a voltage blocking structure, the edge termination section surrounding the active section; a separation section in an edge area of the semiconductor substrate, the separation section having a device separation structure, the separation section surrounding the edge termination section; the semiconductor device further comprising: a semiconductor region of a second conductivity type in a surface portion on a second major surface side of the semiconductor substrate, the semiconductor region being disposed beneath each of the active section, the edge termination section and the separation section; a back surface side electrode on the second conductivity type semiconductor region; a first semiconductor region of the second conductivity type in a surface portion on a first major surface side of the semiconductor substrate, an insulator film on the first semiconductor the region; a trench formed from the second major surface side of the semiconductor substrate; a second semiconductor region of the second conductivity type formed along a side wall of the trench, the second semiconductor region being in contact with the semiconductor region which is disposed beneath each of the active section, the edge termination section and the separation section and with the first semiconductor region; and the second semiconductor region comprising a boundary portion between the side wall of the trench in an opening thereof and a second major surface of the semiconductor substrate, wherein either (i) the boundary portion of the second semiconductor region is wider than another portion of the second semiconductor region excluding the boundary portion or (ii) the boundary portion of the second semiconductor region is doped more heavily than the other portion of the second semiconductor region.