Semiconductor device and manufacturing method of semiconductor device

A semiconductor device comprising:

• a semiconductor substrate including a drift region of a first conductivity type;
• an emitter region of the first conductivity type provided above the drift region inside the semiconductor substrate and having a doping concentration higher than a doping concentration of the drift region;
• a base region of a second conductivity type provided between the emitter region and the drift region inside the semiconductor substrate;
• an accumulation region of the first conductivity type provided between the base region and the drift region inside the semiconductor substrate and having a doping concentration higher than the doping concentration of the drift region;
• and
• a plurality of trench portions provided from an upper surface of the semiconductor substrate to an inside of the semiconductor substrate and including a gate trench portion and one or more dummy trench portions, wherein
• in a first mesa portion sandwiched by two trench portions among the plurality of trench portions, a depth of the accumulation region from the upper surface of the semiconductor substrate reaches at least a range of bottom ⅛ of a depth of the gate trench portion, wherein at least one of the two trench portions is the gate trench portion.