Semiconductor device

A semiconductor device comprising:

• a first conductivity type semiconductor substrate to be a drain area;
• a drift area formed on the drain area;
• a second conductivity type body area formed on an upper portion of the drift area;
• a first conductivity type source area formed on an upper portion of the body area;
• a trench that penetrates the source area and the body area, and reaches the drift area;
• an insulation film formed on an inner wall of the trench;
• a gate electrode formed inside the insulation film;
• and
• a second conductivity type back gate electrode formed inside the body area and electrically connected with the body area,
• wherein:
• a current flows from the drain area to the source area in a state where a first voltage is applied to the drain area, a second voltage lower than the first voltage is applied to the source area and the body area, and a third voltage equal to or higher than a first threshold is applied between the gate electrode and the source area,
• a current flows from the source area to the drain area in a state where the first voltage is applied to the source area, the second voltage is applied to the drain area and the body area, and a fourth voltage equal to or higher than a second threshold is applied between the gate electrode and the drain area,
• a sheet resistance of the back gate electrode is lower than a sheet resistance of the body area, and
• the source area and the back gate electrode are disposed apart from each other with a clearance sufficient for preventing a breakdown phenomenon caused between the source area and the back gate electrode when a maximum operation voltage is applied between the source area and the drain area.