A thin film transistor includes a source electrode, a drain electrode, a semiconducting layer, an insulating layer, and a gate electrode. The drain electrode is spaced from the drain electrode. The semiconducting layer is electrically connected to the drain electrode and the source electrode. The semiconducting layer is an oxide semiconductor film comprising indium (In), cerium (Ce), zinc (Zn) and oxygen (O) elements, and a molar ratio of In, Ce, and Zn as In:Ce:Zn is in a range of 2:(0.5 to 2):1. The gate electrode is insulated from the semiconducting layer, the source electrode, and the drain electrode by the insulating layer.
