Patent ID: 8686500

Claim:
A double diffused metal oxide semiconductor (DMOS) device formed in a first conductive type substrate, wherein the substrate has an upper surface, the DMOS device comprising: a second conductive type high voltage well, which is formed beneath the upper surface; a field oxide region, which is formed on the upper surface, and is located in the high voltage well from top view; a gate, which is formed on the upper surface, wherein part of the gate is above the field oxide region; a second conductive type source and a second conductive type drain, which are formed at two sides of the gate beneath the upper surface respectively, wherein the drain and the source are separated by the gate and the field oxide region from top view, and the drain is formed in the high voltage well; a first conductive type body region, which is formed in the substrate beneath the upper surface, wherein the source is in the body region; and a first conductive type deep well, which is formed beneath and adjacent to the high voltage well in a vertical direction, wherein the deep well is defined by a same lithography process step as the high voltage well, and the deep well and the high voltage well have a same area size from top view.