A semiconductor substrate includes a first-conductivity drift layer, a first-conductivity first impurity layer, a second-conductivity base layer, and a first-conductivity first emitter region. The first impurity layer is provided on the drift layer, and has impurity concentration higher than impurity concentration of the drift layer. The base layer is provided on the first impurity layer. The first emitter region is provided on the base layer. The first impurity layer connects between trenches. The plurality of trenches are formed in the semiconductor substrate covered by a gate insulation film. The gate insulation film has a first thickness between a gate electrode and the drift layer in a side wall surface, and has a second thickness between the gate electrode and the drift layer in a bottom surface. The second thickness is larger than the first thickness.