A semiconductor device includes an n-type drain layer, an n-type base layer provided on the n-type drain layer, a p-type base layer and an n-type source layer partially formed in surface layer portions of the n-type base layer and the p-type base layer, respectively, a gate insulation film formed on a surface of the p-type base layer between the n-type source layer and the n-type base layer, a gate electrode formed on the gate insulation film facing the p-type base layer across the gate insulation film, a p-type column layer formed within the n-type base layer to extend from the p-type base layer toward the n-type drain layer, a depletion layer alleviation region arranged between the p-type column layer and the n-type drain layer and including first baryons converted to donors, a source electrode connected to the n-type source layer, and a drain electrode connected to the n-type drain layer.