A thin film transistor includes a gate electrode, a gate insulating layer, a channel layer, an etching stop layer, two contact holes, a source, and a drain. The gate insulating layer covers the gate electrode. The channel layer is arranged on the gate insulating layer corresponding to the gate electrode. The etching stop layer covers the channel layer and includes an organic stop layer and a hard mask layer, the hard mask layer is located on a surface of the organic stop layer opposite to the channel layer to enhance a hardness of the organic stop layer. The two contact holes pass through the etching stop layer. The source connects to the channel via one contact hole, and the drain connects to the channel via the other contact hole.