Integrated mos power transistor with poly field plate extension for depletion assist

Abstract

A split gate power transistor includes a doped substrate, a gate oxide layer on the substrate, and a split polysilicon layer over the gate oxide layer, which forms a polysilicon gate and a polysilicon field plate. The two polysilicon portions are separated by a gap. The field plate is electrically coupled to a source of the split gate power transistor. One or more polysilicon extension tabs extend from the field plate to at least above the edge of the first doped region. The polysilicon gate is cut to form a cut-out region for the end of each polysilicon extension tab extending toward the body substrate. The one or more polysilicon extension tabs force the portion of the transition region underneath the field plate into deep-depletion, thereby preventing the formation of a hole inversion layer in this region.