High-voltage lateral DMOS device

A lateral DMOS device formed in a semiconductor substrate of a first conductivity type, the substrate not comprising an epitaxial layer, the device comprising:

• a field oxide layer at a surface of the substrate, the field oxide layer having first and second edges;
• a conformal drift region of a second conductivity type in the substrate, the drift region comprising a shallow portion, a first deep portion and a second deep portion, each of the first and second deep portions and the shallow portion extending downward from the surface of the substrate, each of the first and second deep portions extending deeper into the substrate than the shallow portion, the entire shallow portion being located directly below the field oxide region, the first deep portion being located on one side of the shallow portion and not directly below the field oxide region, the second deep portion being located on an opposite side of the shallow portion and not directly below the field oxide region;
• a body region of the first conductivity type located adjacent the surface of the substrate and adjacent the first deep portion of the drift region;
• a source region of the second conductivity type formed adjacent the surface of the substrate and adjacent the body region, the source region being separated from the first deep portion of the drift region by a channel region;
• a gate dielectric layer and a gate overlying the channel region;
• and
• a drain region of the second conductivity type adjacent the surface of the substrate and adjacent the second deep portion of the drift region;
• wherein the drift region comprises a vertical series of dopant regions of the second conductivity type having different doping concentrations;
• and
• wherein a peak doping concentration of a first one of the dopant regions deeper in the substrate is greater than a peak doping concentration of a second one of the dopant regions shallower in the substrate and the first one of the dopant regions is included in both the first deep portion of the drift region and the shallow portion of the drift region but the second one of the dopant regions is included in the first deep portion of the drift region but does not extend into the shallow portion of the drift region.