US Patent 11342453 Field effect transistor with asymmetric gate structure and method

Disclosed is a lateral double-diffused metal oxide semiconductor field effect transistor (LDMOSFET) with a replacement metal gate (RMG) structure that includes a first section, which traverses a semiconductor body at a channel region in a first-type well, and a second section, which is adjacent to the first section and which traverses the semiconductor body at a drain drift region in a second-type well. The RMG structure includes, in both sections, a first-type work function layer and a second-type work function layer on the first-type work function layer. However, the thickness of the first-type work function layer in the first section is greater than the thickness in the second section such that the RMG structure is asymmetric. Thus, threshold voltage (Vt) at the first section is greater than Vt at the second section and the LDMOSFET has a relatively high breakdown voltage (BV). Also disclosed are methods for forming the LDMOSFET.