Stepped-source LDMOS architecture

A semiconductor device, comprising:

• a semiconductor region including a first conductivity type having a first doping profile;
• a source region near a working top surface of the semiconductor region;
• a drain region near the working top surface and laterally offset from the source region;
• a body region near the working top surface, the body region comprising the first conductivity type having a second doping profile;
• a gate located above the working top surface and located laterally between the source and drain regions, the gate including a polysilicon portion and a first oxide spacer at a lateral edge of the gate;
• and
• a drift region located laterally between the gate and the drain region and at least partially overlapping with the gate and drain regions, the drift region comprising:
• a shallow portion extending laterally from the drain region toward the gate, the shallow portion comprising the second conductivity type having a peak doping concentration greater than an average drift region doping concentration;
• and
• a deep portion located at a greater depth within the semiconductor region than the shallow region, the deep portion comprising the second conductivity type having a peak doping concentration less than the average drift region doping concentration;
• wherein the deep portion extends laterally from the drain region toward the gate but not as far as the shallow portion;
• and
• wherein the shallow and deep portions are vertically separated along at least a portion of their overlapping width by a region of the first conductivity type in the lateral region extending from the gate toward the drain region;
• wherein the source region and the gate at least partially laterally overlap the body region near the working top surface;
• wherein the lateral location of an upper portion of the shallow portion of the drift region near the first oxide spacer is determined at least in part by the location of the first oxide spacer;
• and
• wherein the shallow portion includes a lower portion extending further under the lateral edge of the gate than the upper portion.