Patent ID: 7977715

Claim:
An LDMOS device comprising: a) a substrate of a first conductivity type; b) an epitaxial layer on said substrate; c) a buried well of a second conductivity type opposite to said first conductivity type in a lower portion of said epitaxial layer, said epitaxial layer being of said first conductivity type below said buried well; d) a field oxide located between a drain and both a gate on a gate oxide and a source; e) a saddle shaped vertical doping gradient of said second conductivity type in said epitaxial layer above said buried well such that the dopant concentration in said epitaxial layer above said buried well and below a central portion of said field oxide is lower than the dopant concentration at the edges of said field oxide nearest said drain and nearest said gate; and f) a P well located in a source region and an N well located in a drain region.