We report here a novel method of fabricating oxide semiconductors via a solid-phase crystallization from amorphous phase. By introducing a large amount of nitrogen atoms to the sputtering atmosphere, the amorphous phase is obtained, where the resultant films are amorphous oxynitride. Since the bonding energy is different between metal-oxygen and metal-nitrogen, solid-phase crystallization is achieved by annealing of amorphous oxynitride films in the oxidization atmosphere at adequate temperatures. The resultant oxide films are highly orientated even on quartz glass substrates and the crystallinity is higher than the films prepared by conventional sputtering deposition. The fabrication method proposed here is very promising for oxide films, especially for the oxide such as zinc oxide and indium (tin) oxide whose amorphous phase is difficult to be obtained.