Semiconductor device

A semiconductor device comprising:

• a semiconductor substrate including a first-conductivity-type drift region;
• a second-conductivity-type base region provided above the drift region inside the semiconductor substrate;
• an accumulation region provided between the drift region and a lower surface of the base region inside the semiconductor substrate, the accumulation region having a lower second-conductivity-type carrier mobility than the drift region and the base region;
• a gate trench portion provided from an upper surface of the semiconductor substrate to an inside of the semiconductor substrate, the gate trench portion being in contact with the base region;
• and
• a carrier passage region occupying at least a partial region between the accumulation region and the gate trench portion inside the semiconductor substrate, the carrier passage region having a higher second-conductivity-type carrier mobility than the accumulation region,
• wherein the gate trench portion includes:
• an upper portion in direct contact with the upper surface of the semiconductor substrate;
• and
• a lower portion provided under the upper portion and narrower than the upper portion,
• the base region is in direct contact with the upper portion,
• the accumulation region is provided at a position facing the lower portion, and
• the carrier passage region is provided between the accumulation region and the lower portion.