Semiconductor memory device and method of manufacturing semiconductor memory device

A method of manufacturing a semiconductor memory device comprising:

• preparing a SOI substrate including a semiconductor substrate of a first conductivity type, an insulation layer provided on the semiconductor substrate, and a semiconductor layer of the first conductivity type provided on the insulation layer;
• forming a gate insulation film on the semiconductor layer;
• forming a gate electrode on the gate insulation film;
• and
• forming a source layer of the first conductivity type and a drain layer of the first conductivity type reaching the insulation layer by implanting impurities of the first conductivity type into the semiconductor layer, wherein
• the conductivity type of the semiconductor layer between the source layer and the drain layer is maintained in the first conductivity type.

A method of manufacturing a semiconductor memory device comprising:

• preparing a SOI substrate including a semiconductor substrate of a second conductivity type, an insulation layer provided on the semiconductor substrate, and a semiconductor layer of the second conductivity type provided on the insulation layer;
• changing the conductivity type of the semiconductor layer and the semiconductor substrate, which are located adjacent to the insulation layer, to a first conductivity type by implanting impurities of a first conductivity type, so that the impurities go through the semiconductor layer and the insulation layer to reach the semiconductor substrate;
• forming a gate insulation film on the semiconductor layer;
• forming a gate electrode on the gate insulation film;
• forming a source layer of the first conductivity type and a drain layer of the first conductivity type by implanting impurities of the first conductivity type in the semiconductor layer.