Patent ID: 8039906

Claim:
A high-voltage metal oxide semiconductor device comprising: a main body of a first conductivity type; a gate conductive layer, extended along an upper surface of the main body; two first wells of a second conductivity type, located in the main body corresponding to two opposite edges of the gate conductive layer; two source regions of the first conductivity type, located in the two first wells respectively and beneath the two opposite edges of the gate conductive layer; a second well of the second conductivity type, which is located in the main body and extended beneath the gate conductive layer to a place close to a substrate, being electrically connected to a gate electrode or a source electrode and away from the two first wells with a predetermined distance, and a distance between the second well and the gate conductive layer being greater than depth of the first well; and a guard ring of the second conductivity type, located in the main body and surrounding the first wells, a depth of the guard ring being greater than that of the depth of the first well, and a lower edge of the guard ring being connected to the second well.