MULTIPLE WELL DRAIN ENGINEERING FOR HV MOS DEVICES

摘要

At least one N-well implant having a different doping level is formed in a silicon substrate by first etching the substrate with an alignment target for aligning future process masks thereto. This alignment target is outside of any active device area. By using at least one N-well implant having a different doping level in combination with the substrate, a graded junction in the drift area of a metal oxide semiconductor (MOS) field effect transistor (FET) can be created and a pseudo Ldd structure may be realized thereby.