Semiconductor device and power converter

A semiconductor device comprising:

• a semiconductor substrate of a first conductivity type;
• gate trenches formed on an upper surface side of the semiconductor substrate;
• gate electrodes embedded in the gate trenches;
• a gate insulating film interposed between the gate electrodes and the semiconductor substrate;
• a channel layer of a second conductivity type formed in a surface portion on the upper surface side of the semiconductor substrate;
• a contact layer of the second conductivity type formed in a surface portion of the channel layer and having a higher peak impurity concentration than the channel layer;
• an emitter layer of the first conductivity type formed adjacent to the gate trenches in the surface portion of the channel layer;
• a carrier storage layer of the first conductivity type formed below the channel layer;
• a collector layer of the second conductivity type formed on a lower surface side of the semiconductor substrate;
• a dummy gate trench formed between each two adjacent ones of the gate trenches on the upper surface side of the semiconductor substrate;
• dummy gate electrodes embedded in the dummy gate trenches;
• and
• a dummy gate insulating film interposed between the dummy gate electrodes and the semiconductor substrate, wherein
• a relationship D4<D1<D3<D2 holds true,
• where D1 is a depth of bottoms of the gate electrodes, D2 is a depth of bottoms of the dummy gate electrodes, D3 is a depth of a bottom of the carrier storage layer, and D4 is a depth of a junction between the channel layer and the carrier storage layer.