At any timing after formation of gate electrodes, particle beam irradiation is performed to a semiconductor wafer having an n−-type drift region constituted by an n−-type epitaxial layer and having an n-type impurity concentration that is higher than a target majority carrier concentration (design value) of the n−-type drift region. Point defects of a defect density corresponding to an irradiation dose of the particle beam are generated in the n−-type drift region by the particle beam irradiation, whereby an effective majority carrier concentration of the n−-type drift region is adjusted and reduced with respect to the n-type impurity concentration of the n−-type drift region, to approach the design value. After formation of the n−-type epitaxial layer, the n-type impurity concentration of the n−-type drift region may be measured, or the n−-type epitaxial layer may be formed to have an n-type impurity concentration higher than the design value.