High quality ZnO:Al (AZO) films have been obtained by our novel fabrication method utilizing solid-phase crystallized (SPC) seed layers. The crystal grain size of AZO films with seed layers is 5 times larger than that of conventional films, which is due to the low nuclei density of seed layers. As a result, the resistivity of AZO films of 18 nm in total film thickness is drastically reduced from 40×10-4Ωcm for the conventional films to 5×10-4Ωcm for our films. No differences in transparency hve been observed between AZO films with and without seed layers and their optical transmittance is higher than 80% in a wide wavelength range of 400-2500 nm. These results reveal that our method is very promising for fabrication of transparent conducting oxide films. Our method opens up a new avenue for oxide fabrications of nm thick films with excellent crystallinity, because it can be easily extended to other oxides whose amorphous phase is difficult to obtain.