Semiconductor device and method for manufacturing semiconductor device
A MOSFET includes a semiconductor substrate having a trench formed in a main surface, a gate oxide film, a gate electrode, and a source interconnection. A semiconductor substrate includes an n-type drift layer and a p-type body layer. The trench is formed to penetrate the body layer and to reach the drift layer. The trench includes an outer peripheral trench arranged to surround an active region when viewed two-dimensionally. On the main surface opposite to the active region when viewed from the outer peripheral trench, a potential fixing region where the body layer is exposed is formed. The source interconnection is arranged to lie over the active region when viewed two-dimensionally. The potential fixing region is electrically connected to the source interconnection.
1. A semiconductor device, comprising:
a semiconductor substrate having a trench formed in one main surface;
a first insulating film arranged on and in contact with a wall surface of said trench;
a gate electrode arranged on and in contact with said first insulating film; and
a first interconnection arranged on said one main surface,
said semiconductor substrate including
a drift layer having a first conductivity type, and
a body layer having a second conductivity type, which is arranged on a side of said one main surface when viewed from said drift layer,
said trench being formed to penetrate said body layer and to reach said drift layer,
said trench including an outer peripheral trench arranged to surround an active region when viewed two-dimensionally,
a potential fixing region where said body layer is exposed being formed in said one main surface opposite to said active region when viewed from said outer peripheral trench,
said first interconnection being arranged to lie over said active region when viewed two-dimensionally, and
said potential fixing region being electrically connected to said first interconnection.
2. The semiconductor device according to claim 1 , wherein
in a region of said drift layer in contact with said outer peripheral trench, an electric field relaxing region having the second conductivity type is formed, and
said electric field relaxing region is connected to said potential fixing region.
3. The semiconductor device according to claim 1 , further comprising:
a second insulating film arranged above said potential fixing region; and
a second interconnection arranged above said second insulating film, wherein
said potential fixing region includes a potential fixing region extension portion extending to a portion below said first interconnection,
said gate electrode includes a gate electrode extension portion extending to a portion below said second interconnection,
said potential fixing region is electrically connected to said first interconnection in said potential fixing region extension portion, and
said gate electrode is electrically connected to said second interconnection in said gate electrode extension portion.
4. The semiconductor device according to claim 1 , further comprising:
a second insulating film arranged above said potential fixing region; and
a second interconnection arranged above said second insulating film, wherein
said first interconnection includes a first interconnection extension portion extending beyond said outer peripheral trench to said potential fixing region,
said second interconnection includes a second interconnection extension portion extending beyond said outer peripheral trench to said gate electrode,
said first interconnection is electrically connected to said potential fixing region in said first interconnection extension portion, and
said second interconnection is electrically connected to said gate electrode in said second interconnection extension portion.
5. The semiconductor device according to claim 1 , wherein
an angle formed between a sidewall surface of said trench and said one main surface is from 100° to 160°.
6. The semiconductor device according to claim 1 , wherein
said semiconductor substrate is composed of silicon carbide.