A semiconductor device includes a gate, a first electrode, a first insulating layer, an active layer, an etching stop layer, a second insulating layer, a source, a drain and a second electrode. The first insulating layer covers the gate and the first electrode. The active layer and the etching stop layer are disposed on the first insulating layer above the gate and the first electrode respectively. The second insulating layer covers the active layer and the etching stop layer and has a first opening and a second opening exposing the active layer and a third opening exposing the etching stop layer. The source and the drain are disposed on the second insulating layer and contact with the active layer through the first opening and the second opening respectively. The second electrode is located on the second insulating layer and contacts with the etching stop layer through the third opening.