Abstract: The purpose of the present invention is to provide an oxide semiconductor thin film, which has relatively high carrier mobility and is suitable as a channel layer material for a TFT, from an oxynitride crystalline thin film. According to the present invention, a crystalline oxynitride semiconductor thin film is obtained by annealing an amorphous oxynitride semiconductor thin film containing In, O, and N or an amorphous oxynitride semiconductor thin film containing In, O, N, and an additional element M, where M is one or more elements selected from among Zn, Ga, Ti, Si, Ge, Sn, W, Mg, Al, Y and rare earth elements, at a heating temperature of 200° C. or more for a heating time of 1 minute to 120 minutes.