A nitride semiconductor device is made using a molecular beam epitaxy growth apparatus having a gas source for supplying a compound including gaseous nitrogen, solid body sources for supplying Group III constituents, and sources for supplying n-type and p-type dopants. A gaseous state compound containing nitrogen, and a Group III constituent is supplied to the surface of a substrate, wherein the substrate is at a temperature of 300.degree. to 1000.degree. C. and is under a pressure of less than 10.sup.-5 Torr, to produce a first layer of oriented polycrystalline nitride semiconductor on the substrate at a growth rate of 0.1 to 20 Angstroms/second. Subsequently, a gaseous state compound containing nitrogen and a Group III constituent is supplied to the surface of the first layer of the substrate to produce a single crystal nitride semiconductor layer on the first layer at a growth rate of 0.1 to 10 Angstroms/second. The resultant nitride semiconductor device comprises a substrate, a first layer of an oriented polycrystalline nitride semiconductor of less than 5000 Angstroms thickness and disposed directly on the substrate, an operating layer of a single crystal nitride semiconductor disposed directly on the first layer, and at least two electrical terminals connected at predetermined locations, with at least one terminal being connected to the first layer.