Patent ID: 7718494

Claim:
A method of forming a semiconductor structure, the method comprising: providing a semiconductor substrate; forming a high-voltage drain metal-oxide-semiconductor (HVD-MOS) device at a surface of the semiconductor substrate comprising: forming a well region of a first conductivity type in the semiconductor substrate; forming an embedded well region in the well region and on a drain side of the HVD-MOS device, wherein the embedded well region is of a second conductivity type opposite the first conductivity type, and wherein the step of forming the embedded well region comprises: performing a first doping step to simultaneously dope the embedded well region and a well region of a core regular MOS device, wherein the core regular MOS device is of the first conductivity type; and performing a second doping step to simultaneously dope the embedded well region and a well region of an I/O regular MOS device, wherein the I/O regular MOS device is of the first conductivity type, wherein during the first doping step, the well region of the I/O regular MOS device is not doped, and wherein during the second doping step, the well region of the core regular MOS device is not doped; and forming a gate stack extending from over the embedded well region to over the well region.