Patent ID: 8754473

Claim:
A power transistor device, comprising: a substrate of a first conductive type; an epitaxial layer of a second conductive type on said substrate and having at least one through hole through said epitaxial layer; a doped base region of said second conductive type in said epitaxial layer; a dopant source layer in said through hole; a doped drain region of said first conductive type in said epitaxial layer at one side of said dopant source layer and contacting said substrate; a first insulating layer on said dopant source layer in said through hole; a gate structure on said first insulating layer in said through hole; a second insulating layer on said gate structure in said through hole; a doped source region of said first conductive type in said doped base region on said doped drain region, wherein said gate structure is between said doped source region and said doped drain region and contacts said doped base region; and a metal layer on said epitaxial layer extending into said through hole to contact said doped source region.