Patent ID: 7911020

Claim:
A semiconductor device comprising: a semiconductor layer of a first conductivity type; an active portion having at least one well region of a second conductivity type selectively positioned in the semiconductor layer; and a breakdown voltage maintaining structure surrounding the active portion, wherein the breakdown voltage maintaining structure comprises: a first semiconductor region of the second conductivity type in the semiconductor layer at an impurity concentration lower than that of at least one well region and higher than that of the semiconductor layer, and surrounding and in contact with an outermost well region among the at least one well region; a plurality of second semiconductor regions of the second conductivity type at the same impurity concentration and with the same diffusion depth as the first semiconductor region in the semiconductor layer, and surrounding the first semiconductor region; a first conductor layer positioned over the first semiconductor region with an insulating film interposed in between; and a plurality of second conductor layers, each positioned over at least one of the second semiconductor regions with the insulating film interposed in between, and spaced from each other, wherein each of the second conductor layers is in contact with one of the second semiconductor regions, wherein the first conductor layer and an innermost second conductor layer among the second conductor layers are spaced from each other, wherein the first conductor layer is in electrical contact with the outermost well region, wherein an innermost second semiconductor region among the second semiconductor regions extends into and is in contact with the first semiconductor region, wherein an inner side end portion of the innermost second conductor layer, which is associated with the innermost second semiconductor region, extends over to the first semiconductor region, wherein at least some of the second semiconductor regions overlap or are in contact with each other.