Extended drain lateral dmos transistor with reduced gate charge and self-aligned extended drain

Abstract

A method to form a LDMOS transistor includes forming a gate/source/body opening and a drain opening in a field oxide on a substrate structure, forming a gate oxide in the gate/source/body opening, and forming a polysilicon layer over the substrate structure. The polysilicon layer is anisotropically etched to form polysilicon spacer gates separated by a space in the gate/source/body opening and a polysilicon drain contact in the drain opening. A body region is formed self-aligned about outer edges of the polysilicon spacer gates, a source region is formed self-aligned about inner edges of the polysilicon spacer gates, and a drain region is formed under the polysilicon drain contact and self-aligned with respect to the polysilicon spacer gates. A drift region forms in the substrate structure between the body region and the drain region, and a channel region forms in the body region between the source region and the drift region.