Patent ID: 8492835

Claim:
A HV MOSFET device, comprising: a substrate having a first conductivity type; a deep well region constructed in the substrate, and having a second conductivity type different from the first conductivity type, wherein the deep well region comprises a boundary site and a middle site, wherein the boundary site is located around the middle site; a source/body region formed in the deep well region and defining a channel region; a drain region formed in the deep well region; a gate structure arranged between the source/body region and the drain region, wherein the gate structure comprises an insulator layer; and a first doped region formed in the deep well region and disposed under the insulator layer, and having the first conductivity type, wherein there is a first ratio between a dopant dose of the first doped region and a dopant dose of the boundary site of the deep well region, and there is a second ratio between a dopant dose of the first doped region and a dopant dose of the middle site of the deep well region, wherein a percentage difference between the first ratio and the second ratio is smaller than or equal to 5%.