A novel fabrication method of ZnO films utilizing solid-phase crystallized seed layers has been developed. In this method, solid phase crystallization (SPC) is performed by annealing amorphous ZnON films, which are prepared by sputtering of ZnO targets in Ar/N2 mixed gases, in an oxidization atmosphere. The grain size of ZnO films deposited on the seed layers is significant larger than that of ZnO films directly deposited on glass substrates, which is considered to be due to the low grain density of seed layers. By utilizing this technique, the resistivity of ZnO:Al (AZO) films is decreased from 20 × 10-4 Ωcm to 5 × 10-4 Ωcm at the film thickness of 30nm. Furthermore, we observed that SPC seed layers are in-plane aligned when Al2O3 substrates are used, which suggests that the fabrication method proposed here is also promising for synthesizing epitaxial ZnO films.