Patent ID: 7791132

Claim:
A power transistor comprising: a drain which comprises a substrate of a first conductivity type; a mesa of the first conductivity type having first and second sidewalls, the substrate comprising a bottom portion of the mesa, an upper portion of the mesa comprising a source, a drift region comprising a middle portion of the mesa, the drift region extending in a vertical direction from the drain to the source, the drift region comprising first and second sections having first and second doping concentration gradients, respectively, the first section extending a first vertical distance below the source and having a lowest doping concentration nearest the source and a highest doping concentration farthest from the source, the second section being disposed beneath the first section and having a lowest doping concentration nearest the first section and a highest doping concentration farthest from the first section, the highest doping concentration of the first section being substantially the same as the lowest doping concentration of the second section, the source having a doping concentration greater than the lowest doping concentration of the first section; and first and second field plate members respectively disposed on opposite sides of the drift region, each of the field plate members being respectively insulated from the first and second sidewalls of the mesa by a dielectric material, the first and second field plate members also being insulated from the substrate, the first and second field plate members extending in the vertical direction from adjacent the upper portion to adjacent the bottom portion of the mesa.