| 摘要 |
PROBLEM TO BE SOLVED: To solve the problems that, when an UMOSFET is manufactured on a silicon carbide wafer, the thickness of a formed oxide film varies with different surface orientations of a trench side surface for formation of a trench gate, and that the surface of the oxide film converted from a polycrystalline silicon has poor planarity, and to increase the dielectric strength, by improving the planarity of the surface of the oxide film. SOLUTION: An n-type drift layer 2, a p-type base layer 3, and an n-type source layer 4 are grown epitaxially and are sequentially formed by a thermal CVD method on an n-type 4H-SiC or 6H-SiC substrate 1. The substrate 1 is vertically etched by reactive ion etching down to such a depth that the source layer 4 and the base layer 3 can be completely removed, to thereby form a trench 11. An amorphous silicon film 14 of an amorphous structure is formed by a low-pressure CVD method on the uneveness surface of the substrate including the trench 11. The substrate is then baked under an nitrogen atmosphere so that the amorphous silicon film 14 is polycrystallized in a solid phase, thus forming a polycrystalline silicon film 16. Subsequently, the substrate is oxidized under an atmospheric-pressure atmosphere to convert the polycrystalline silicon film 16 to an oxide film 15. COPYRIGHT: (C)2007,JPO&INPIT
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