In the fabrication of transparent conductive oxide thin film transistor (TFT), an atomic layer deposited (ALD) zinc oxide (ZnO) and a cross-linked poly-vinyl-alcohol (c-PVA) were each used as active layer and gate insulating layer on poly-ethylene (PET) substrate respectively. Considering the transmittance and the deposition rate of the ALD ZnO at a low temperature without any damage on PET substrate, the ZnO layer was deposited at a temperature of 120 degrees C on a spin-coated c-PVA layer. From the atomic force microscope (AFM) images, it was possible to conclude that the surface morphologies of ZnO deposited on a c-PVA layer was not inferior to those of ZnO deposited on bare-Si and that the c-PVA can be used as a gate insulator at 120 degrees C. The fabricated ZnO TFT showed good electrical characteristics such as the mobility of 0.1cm2/V center dot s, on-off current ratio of 4.5x104.