A semiconductor device includes a plurality of broad buffer layers provided in a drift layer. Each of the plurality of the broad buffer layers has an impurity concentration exceeding that of a portion of the drift layer excluding the broad buffer layers, and has a mountain-shaped impurity concentration distribution in which a local maximum value is less than the impurity concentration of an anode layer and a cathode layer. The plurality of broad buffer layers are disposed at different depths from a first main surface of the drift layer, respectively, the number of broad buffer layers close to the first main surface from the intermediate position of the drift layer is at least one, and number of broad buffer layers close to a second main surface of the drift layer from the intermediate position of the drift layer is at least two. The broad buffer layer includes a hydrogen-related donor.

A p anode layer is formed on one main surface of an n.sup. drift layer. N.sup.+ cathode layer having an impurity concentration more than that of the n.sup. drift layer is formed on the other main surface. An anode electrode is formed on the surface of the p anode layer. A cathode electrode is formed on the surface of the n.sup.+ cathode layer. N-type broad buffer region having a net doping concentration more than the bulk impurity concentration of a wafer and less than the n.sup.+ cathode layer and p anode layer is formed in the n.sup. drift layer. Resistivity .sub.0 of the n.sup. drift layer satisfies 0.12V.sub.0.sub.00.25V.sub.0 with respect to rated voltage V.sub.0. Total amount of net doping concentration of the broad buffer region is equal to or more than 4.810.sup.11 atoms/cm.sup.2 and equal to or less than 1.010.sup.12 atoms/cm.sup.2.

A p anode layer is formed on one main surface of an n.sup. drift layer. N.sup.+ cathode layer having an impurity concentration more than that of the n.sup. drift layer is formed on the other main surface. An anode electrode is formed on the surface of the p anode layer. A cathode electrode is formed on the surface of the n.sup.+ cathode layer. N-type broad buffer region having a net doping concentration more than the bulk impurity concentration of a wafer and less than the n.sup.+ cathode layer and p anode layer is formed in the n.sup. drift layer. Resistivity .sub.0 of the n.sup. drift layer satisfies 0.12V.sub.0.sub.00.25V.sub.0 with respect to rated voltage V.sub.0. Total amount of net doping concentration of the broad buffer region is equal to or more than 4.810.sup.11 atoms/cm.sup.2 and equal to or less than 1.010.sup.12 atoms/cm.sup.2.

A p anode layer is formed on one main surface of an n.sup. drift layer. N.sup.+ cathode layer having an impurity concentration more than that of the n.sup. drift layer is formed on the other main surface. An anode electrode is formed on the surface of the p anode layer. A cathode electrode is formed on the surface of the n.sup.+ cathode layer. N-type broad buffer region having a net doping concentration more than the bulk impurity concentration of a wafer and less than the n.sup.+ cathode layer and p anode layer is formed in the n.sup. drift layer. Resistivity .sub.0 of the n.sup. drift layer satisfies 0.12V.sub.0.sub.00.25V.sub.0 with respect to rated voltage V.sub.0. Total amount of net doping concentration of the broad buffer region is equal to or more than 4.810.sup.11 atoms/cm.sup.2 and equal to or less than 1.010.sup.12 atoms/cm.sup.2.

A p anode layer is formed on one main surface of an n.sup. drift layer. N.sup.+ cathode layer having an impurity concentration more than that of the n.sup. drift layer is formed on the other main surface. An anode electrode is formed on the surface of the p anode layer. A cathode electrode is formed on the surface of the n.sup.+ cathode layer. N-type broad buffer region having a net doping concentration more than the bulk impurity concentration of a wafer and less than the n.sup.+ cathode layer and p anode layer is formed in the n.sup. drift layer. Resistivity .sub.0 of the n.sup. drift layer satisfies 0.12V.sub.0.sub.00.25V.sub.0 with respect to rated voltage V.sub.0. Total amount of net doping concentration of the broad buffer region is equal to or more than 4.810.sup.11 atoms/cm.sup.2 and equal to or less than 1.010.sup.12 atoms/cm.sup.2.

A III-nitride tunnel junction with a modified p-n interface, wherein the modified p-n interface includes a delta-doped layer to reduce tunneling resistance. The delta-doped layer may be doped using donor atoms comprised of Oxygen (O), Germanium (Ge) or Silicon (Si); acceptor atoms comprised of Magnesium (Mg) or Zinc (Zn); or impurities comprised of Iron (Fe) or Carbon (C).

A III-nitride tunnel junction with a modified p-n interface, wherein the modified p-n interface includes a delta-doped layer to reduce tunneling resistance. The delta-doped layer may be doped using donor atoms comprised of Oxygen (O), Germanium (Ge) or Silicon (Si); acceptor atoms comprised of Magnesium (Mg) or Zinc (Zn); or impurities comprised of Iron (Fe) or Carbon (C).

A tunnel field effect transistor includes a constant current formation layer, a source region and a drain region provided on the constant current formation layer, a channel layer provided between the source region and the drain region, a gate electrode provided on the channel layer, and a gate insulating film provided between the gate electrode and the channel layer, wherein the source region and the drain region have different conductivity types, and the constant current formation layer forms a constant current between the drain region and the constant current formation layer.

A III-nitride tunnel junction with a modified p-n interface, wherein the modified p-n interface includes a delta-doped layer to reduce tunneling resistance. The delta-doped layer may be doped using donor atoms comprised of Oxygen (O), Germanium (Ge) or Silicon (Si); acceptor atoms comprised of Magnesium (Mg) or Zinc (Zn); or impurities comprised of Iron (Fe) or Carbon (C).

A III-nitride tunnel junction with a modified p-n interface, wherein the modified p-n interface includes a delta-doped layer to reduce tunneling resistance. The delta-doped layer may be doped using donor atoms comprised of Oxygen (O), Germanium (Ge) or Silicon (Si); acceptor atoms comprised of Magnesium (Mg) or Zinc (Zn); or impurities comprised of Iron (Fe) or Carbon (C).