SILICON CARBIDE SEMICONDUCTOR DEVICE MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a silicon carbide semiconductor device manufacturing method which can ensure sufficient insulation reliability of a gate insulation film while achieving low channel resistance.SOLUTION: A silicon carbide semiconductor device manufacturing method comprises steps of: preparing a mask layer 100 for covering a principal surface 10a which is a carbon surface or a surface cut off at an angle of equal to or less than 8 degrees with a two-layer structure of a thermally oxidized film 110 and a deposited oxide film 120 with a density lower than that of the thermally oxidized film 110; and forming a trench TR by performing thermal etching on the principal surface 10a at an opening of the mask layer 100. During thermal etching, since a gap GP is formed between an edge which surrounds an opening of the thermally oxidized film 110 and the principal surface 10a is formed by stress applied to the thermally oxidized film 110 due to thermal contraction of the deposited oxide film 120, side etching at the gap GP is accelerated. A thickness of a gate insulation film formed by thermal oxidation of the silicon carbide substrate 10 where the trench TR is formed is decreased at a side surface SW1 of the trench TR but increased at a side surface SW2 in accordance with plane orientation dependence property of thermal oxidation speed.