A semiconductor device includes a base substrate. A first thin-film transistor is disposed on the base substrate. The first thin-film transistor includes a first input electrode, a first output electrode, a first semiconductor pattern disposed below a first insulating layer, and a first control electrode disposed on the first insulating layer and below a second insulating layer. A second thin-film transistor includes a second input electrode, a second output electrode, a second semiconductor pattern disposed on the second insulating layer, and a second control electrode disposed on an insulating pattern formed on the second semiconductor pattern and exposes a portion of the second semiconductor pattern. The first semiconductor pattern includes a crystalline semiconductor. The second semiconductor pattern includes an oxide semiconductor. The first semiconductor pattern, the first control electrode, the second semiconductor pattern, and the second control electrode are overlapped.