Patent ID: 8164139
Filing Date: 2012-04-24
Classification: H01L

Abstract:
1. A trench MOSFET structure with a guard ring, comprising: a substrate of a first conductivity doping type including an epitaxial layer of said first conductivity doping type formed on said substrate, said epitaxial layer having a doping concentration less than that of said substrate; a plurality of source regions of said first conductivity doping type formed in said epitaxial layer, and a plurality of first type body regions of a second conductivity doping type formed beneath said sources in an active area; an insulating layer formed on said epitaxial layer; a plurality of first type trenches in said active area vertically penetrating through said insulating layer and said source regions, and extending into said body regions, said first type trenches having an gate oxide layer formed thereon, said first type trenches being filled with a doped polysilicon layer as trenched contact gates for current conduction; a guard ring being formed in said trenched contact gate area and said termination area, said guard ring extending from a top surface of said epitaxial layer having said second conductivity doping type, said guard ring having a junction depth deeper than that of said body region, and said guard ring wrapping around a sidewall and a bottom of said trenched contact gate; at least one second type trench having said gate oxide layer formed thereon, said second type trench being deeper and wider than said first type trench, said second type trench extending from a surface of said body regions into said guard ring region, said second type trench being filled with said doped polysilicon as a trenched contact gate between said active area and a termination area; said guard ring having doping concentration gradually decreasing from a sidewall of said second type trenched contact gate toward a center of said bottom of said second type trenched contact gate; a drift region of said first conductivity doping being formed between said substrate and said guard ring, and formed underneath said second type trenched contact gate, a height of said drift region under said center of said bottom of said second type trenched contact gate being greater than those heights of said drift region under said sidewall of said second type trenched contact gate, the height of said drift region being defined by a distance from said substrate to said guard ring; a second type body region with said second conductivity doping type formed between said active area and said trenched contact gate; and a third type body region with said second conductivity doping type formed in said termination area.