A semiconductor diode comprising: a first conductivity type silicon carbide substrate; a first conductivity type drift layer formed on the top surface of the silicon carbide substrate and having a lower impurity concentration than the silicon carbide substrate; a first electrode formed on the rear surface of the substrate; a mesa structure formed on a surface of the drift layer; a second conductivity type electric field relaxation region the conductivity type of which is opposite to the first conductivity type and that is formed in an outer edge region on the outside of the mesa structure on a surface region of the drift layer, and a channel stopper layer formed on the outside of the electric field relaxation region; wherein in the mesa structure, there are formed: an electric charge implantation region of the second conductivity type formed on the drift layer; a resistance reduction region of the second conductivity type formed on the electric charge implantation region; a leakage reduction region of the second conductivity type that is formed at a sidewall portion of the mesa structure and adjacent to the resistance reduction region, the electric charge implantation region, and the electric field relaxation region; wherein the device further comprises a second electrode formed on and making contact with the resistance reduction region; and an insulating film covering the mesa structure and having an opening for the second electrode, the insulating film being adjacent to the leakage reduction region and to the electric field relaxation region, wherein the leakage reduction region extends from the sidewall portion over a corner portion between the sidewall portion and the insulating film to the electric field relaxation region, wherein the impurity concentration of the electric charge implantation region is larger than the impurity concentration of the electric field relaxation region and smaller than the impurity concentration of the resistance reduction region, and wherein the impurity concentration of the leakage reduction region is larger than the impurity concentration of the electric field relaxation region and smaller than the impurity concentration of the resistance reduction region. a first conductivity type silicon carbide substrate; a first conductivity type drift layer formed on the top surface of the silicon carbide substrate and having a lower impurity concentration than the silicon carbide substrate; a first electrode formed on the rear surface of the substrate; a mesa structure formed on a surface of the drift layer; a second conductivity type electric field relaxation region the conductivity type of which is opposite to the first conductivity type and that is formed in an outer edge region on the outside of the mesa structure on a surface region of the drift layer, and a channel stopper layer formed on the outside of the electric field relaxation region; wherein in the mesa structure, there are formed: an electric charge implantation region of the second conductivity type formed on the drift layer; a resistance reduction region of the second conductivity type formed on the electric charge implantation region; a leakage reduction region of the second conductivity type that is formed at a sidewall portion of the mesa structure and adjacent to the resistance reduction region, the electric charge implantation region, and the electric field relaxation region; an electric charge implantation region of the second conductivity type formed on the drift layer; a resistance reduction region of the second conductivity type formed on the electric charge implantation region; a leakage reduction region of the second conductivity type that is formed at a sidewall portion of the mesa structure and adjacent to the resistance reduction region, the electric charge implantation region, and the electric field relaxation region; wherein the device further comprises a second electrode formed on and making contact with the resistance reduction region; and an insulating film covering the mesa structure and having an opening for the second electrode, the insulating film being adjacent to the leakage reduction region and to the electric field relaxation region, wherein the leakage reduction region extends from the sidewall portion over a corner portion between the sidewall portion and the insulating film to the electric field relaxation region, wherein the impurity concentration of the electric charge implantation region is larger than the impurity concentration of the electric field relaxation region and smaller than the impurity concentration of the resistance reduction region, and wherein the impurity concentration of the leakage reduction region is larger than the impurity concentration of the electric field relaxation region and smaller than the impurity concentration of the resistance reduction region.