Silicon carbide semiconductor device

A process for producing a semiconductor device using silicon carbide, comprising the steps of:

• preparing a silicon carbide substrate having a surface of a (0001) carbon face;
• forming a trench on the surface of the (0001) carbon face;
• forming a semiconductor layer on bottom and side surfaces of the trench;
• and
• thermally oxidizing the semiconductor layer such that the semiconductor layer formed on the bottom surface of the trench is entirely converted to an oxide layer while the semiconductor layer formed on the side surface of the trench is partially converted to an oxide layer to leave a thinned semiconductor layer interposed between the oxide layer converted from the semiconductor layer on the side surface of the trench and the side surface of the trench.

A process for producing a MOS transistor, comprising the steps of:

• laminating a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type to provide a semiconductor substrate composed of silicon carbide and having a surface of a (0001) carbon face of the second semiconductor layer of the second conductivity type;
• forming a trench extending from the surface to the first semiconductor layer of the first conductivity type;
• forming a third semiconductor layer at least on the bottom and side surfaces of the trench;
• thermally oxidizing the third semiconductor layer such that the third semiconductor layer formed on the bottom surface of the trench is entirely converted to an oxide layer while the third semiconductor layer formed on the side surface of the trench is partially converted to an oxide layer as a gate oxide layer of a MOS transistor to leave a thinned third semiconductor layer as a channel region of the MOS transistor interposed between the oxide layer converted from the third semiconductor layer on the side surface of the trench and the side surface of the trench;
• and
• forming a gate electrode in the trench.