A thin-film transistor comprises a substrate, a first electrode on the top surface of the substrate, an insulation layer on the top surface of the substrate and covering the first electrode, a semiconductor oxide layer on the top surface of the insulation layer, a protection layer on the top surface of the semiconductor oxide layer, an organic dielectric layer on the top surface of the semiconductor oxide layer and covering the protection layer, a source electrode and a drain electrode both penetrating the organic dielectric layer from the top surface thereof. A channel thickness of the semiconductor oxide layer is not thicker than 20 nanometers. The source electrode contacts the semiconductor oxide layer at the first side of the protection layer and the drain electrode contacts the semiconductor oxide layer at the second side, opposite to the first side, of the protection layer.