Semiconductor device and manufacturing method thereof

A semiconductor device having a MOS gate side surface structure, comprising:

• a semiconductor substrate of one conductivity type;
• a substrate insulator film selectively formed on the surface of the semiconductor substrate;
• a deposited semiconductor layer formed on the surface of the semiconductor substrate and the substrate insulator film, the deposited semiconductor layer having a buffer region of the one conductivity type in contact with the surface of the semiconductor substrate, a base region of the other conductivity type adjacent to the buffer region on the substrate insulator film, and an emitter region of the one conductivity type in the base region, the emitter region being at a position holding the surface of the base region between the buffer region and the emitter region;
• a gate electrode of polycrystalline semiconductor on the surface of the buffer region and on the surface of the base region held between the buffer region and the emitter region;
• a gate insulator film held between the gate electrode and the buffer region, and between the gate electrode and the base region;
• an interlayer insulator film covering the gate electrode of the polycrystalline semiconductor;
• and
• an emitter electrode in contact with both the base region and the emitter region.

A method of manufacturing a semiconductor device having a MOS gate side surface structure, the method including the steps of:

• forming a masking insulator film on the surface of a semiconductor substrate of one conductivity type;
• forming a trench in the semiconductor substrate using the masking insulator film as a mask;
• forming a substrate insulator film on the surface of the semiconductor substrate, including the trench;
• depositing a polycrystalline semiconductor layer to a thickness more than the depth of the trench;
• smoothing the surface of the polycrystalline semiconductor layer by grinding the surface of the polycrystalline semiconductor layer until the surface of one of the masking insulator film or the substrate insulator film becomes exposed;
• forming a gate insulator film on the surface of the semiconductor substrate;
• removing all insulator films layered at the position of the masking insulator film to expose the surface of the semiconductor substrate;
• depositing a semiconductor layer of the one conductivity type on the exposed semiconductor substrate and the gate insulator film so that the semiconductor layer contacts the surface of the exposed semiconductor substrate;
• forming a base region of the other conductivity type and an emitter region of the one conductivity type in the deposited semiconductor layer, the base region being formed adjacent to a region of the deposited semiconductor layer in contact with the semiconductor substrate, the region being provided as a buffer region of the one conductivity type, and the emitter region being formed adjacent to the base region on the side opposite to the buffer region;
• and
• forming an emitter electrode covering the buffer region with an interlayer insulator film between and in contact with both the base region of the other conductivity type and the emitter region.

A method of manufacturing a semiconductor device having a MOS gate side surface structure, the method including the steps of:

• forming a substrate insulator film selectively covering the surface of a semiconductor substrate of one conductivity type;
• depositing a polycrystalline semiconductor layer;
• removing part of the polycrystalline semiconductor layer in contact with the surface of the semiconductor substrate;
• forming a gate insulator film;
• exposing the surface of the semiconductor substrate by removing part of the gate insulator film in contact with the surface of the semiconductor substrate;
• depositing a semiconductor layer of the one conductivity type on the exposed surface of the semiconductor substrate;
• forming in the semiconductor layer a base region of the other conductivity type adjacent to a buffer region of the one conductivity type as a region of the semiconductor layer in contact with the semiconductor substrate, and an emitter region of the one conductivity type adjacent to the base region on the side opposite to the buffer region;
• and
• forming an emitter electrode covering the buffer region with an interlayer insulator film between and in contact with both the base region and the emitter region.