Patent ID: 7999315

Claim:
A semiconductor device, comprising: a substrate including a semiconductor region defining a working top surface in which the semiconductor device is formed; a drain region in the semiconductor; a source region in the semiconductor; and a drift region in the semiconductor device, the drift region including at least a portion that is located laterally between the drain region and the source region, the drift region including: a first layer, having a first doping concentration of a first conductivity type, wherein the first layer includes a retrograde doping concentration of the first conductivity type; and a second layer, extending below an underside of the first layer, the second layer having a second higher doping concentration of the first conductivity type than the first layer and configured to allow drift current between the source region and the drain region in the second layer when a depletion region is formed in at least a portion of the first layer between the source region and the drain region.