A method for manufacturing a semiconductor device includes the steps of: forming, on a principal face of a substrate, a semiconductor layer including a first semiconductor region of a first conductivity type; and forming, in the semiconductor layer, a trench having a bottom located in the first semiconductor region. The method further includes a step of forming a trench bottom impurity region being of a second conductivity type and covering the bottom of the trench by performing annealing to cause part of the semiconductor layer corresponding to an upper corner portion of the trench to move to be placed on the bottom of the trench.