Abstract: A seed substrate for epitaxial growth has a support substrate, a planarizing layer of 0.5 to 3 ?m provided on the top surface of the support substrate, and a seed crystal layer provided on the top surface of the planarizing layer. The support substrate includes a core of group III nitride polycrystalline ceramics and a 0.05 to 1.5 ?m encapsulating layer that encapsulates the core. The seed crystal layer is provided by thin-film transfer of 0.1 to 1.5 ?m of the surface layer of Si<111> single crystal with oxidation-induced stacking faults (OSF) of 10 defects/cm2 or less. High-quality, inexpensive seed substrates with few crystal defects for epitaxial growth of epitaxial substrates and solid substrates of group III nitrides such as AlN, AlxGa1-xN (0<X<1) and GaN are obtained.

Abstract: A nitride semiconductor substrate, including a Ga-containing nitride semiconductor thin film formed on a substrate for film-forming in which a single crystal silicon layer is formed above a supporting substrate via an insulative layer, wherein the nitride semiconductor substrate has a region where the Ga-containing nitride semiconductor thin film is not formed inward from an edge of the single crystal silicon layer being a growth surface of the nitride semiconductor thin film. This provides: a nitride semiconductor substrate with inhibited generation of a reaction mark; and a manufacturing method therefor.

Abstract: A method for producing a nitride semiconductor wafer, in which a nitride semiconductor thin film is grown on a silicon single crystal substrate by vapor phase growth, includes, by using a silicon single crystal substrate having a resistivity of 1000 ?·cm or more, an oxygen concentration of less than 1×1017 atoms/cm3 and a thickness of 1000 ?m or more, growing the nitride semiconductor thin film on the silicon single crystal substrate by vapor phase growth. As a result, a method produces a nitride semiconductor wafer in which plastic deformation and warpage are suppressed even in the case of a high-resistivity, ultra-low oxygen concentration silicon single crystal substrate, which is promising as a support substrate for high frequency devices.