A thin film transistor (TFT) structure includes a metal oxide semiconductor layer, a gate, a source, a drain, a gate insulation layer, and a passivation layer. The metal oxide semiconductor layer has a crystalline surface which is constituted by a plurality of grains separated from one another. An indium content of the grains accounts for at least 50% of all metal elements of the metal oxide semiconductor layer. The gate is disposed on one side of the metal oxide semiconductor layer. The source and the drain are disposed on the other side of the metal oxide semiconductor layer. The gate insulation layer is disposed between the gate and the metal oxide semiconductor layer. The passivation layer is disposed on the gate insulation layer, and the crystalline surface of the metal oxide semiconductor layer is in direct contact with the gate insulation layer or the passivation layer.