Patent ID: 8030702

Claim:
A trenched MOSFET with a guard ring and a channel stop, comprising: a substrate of a first conductivity doping type including an epi layer of said first conductivity doping type formed on said top thereof with doping concentration less than said substrate; a plurality of sources of said first conductivity doping type formed in said epi layer and a plurality of body regions of a second conductivity doping type formed beneath said sources in said epi layer; an insulating layer formed on said epi layer; a plurality of a first type trenches vertically extending from a surface of said epi layer into said source and said body regions and having an gate oxide layer formed thereon, the first type trenches being filled with a doped polysilicon layer as trenched gates for current conduction; at least one second type trench having an gate oxide layer formed thereon, the second type trench being deeper and wider than said first type trench vertically extending from said surface of said epi layer into said body regions, said second type trench filled with said doped polysilicon as trenched contact gate; a first metal contact plug penetrating through said insulating layer and extending into said second type trench, said first metal contact plug being connected to a first metal layer formed on said insulating layer, said first metal contact serving as gate metal in a termination area of a chip; a plurality of second metal contact plugs, each penetrating through said insulating layer and one of said source, and extending into said body regions separated by said first type trenches and said second type trenches, said metal contact plugs being connected to a second metal layer formed on said insulating layer, said second metal layer serving as source metal; a guard ring formed in said termination area of said chip, said guard ring extending inwardly from said top surface of said epi layer, said guard ring having a junction depth deeper than that of said body region and contacting said body region with doping concentration less than said body region, said guard ring having said second conductivity doping type and having a doping concentration 10 15 ˜10 17 cm −3 ; and a channel stop region formed beneath said top surface of said epi layer near an edge of said chip, said channel stop region contacting said guard ring in said termination area and having said first conductivity doping type with a doping concentration heavier than said epi layer, wherein said gate metal above said guard ring in said termination area serving as a metal field plate for breakdown voltage enhancement.