A flexible semiconductor device includes an insulating film on which a semiconductor element is formed. The top and bottom surfaces of the insulating film have a top wiring pattern layer and a bottom wiring pattern layer, respectively. The semiconductor element includes a semiconductor layer formed on the top surface of the insulating film, a source electrode and a drain electrode formed on the top surface of the insulating film so as to contact the semiconductor layer, and a gate electrode formed on the bottom surface of the insulating film so as to be opposite the semiconductor layer. A first thickness, which is the thickness of the insulating film facing the source electrode, the drain electrode, the top wiring pattern layer, and the bottom wiring pattern layer, is greater than a second thickness, which is the thickness of the insulating film between the gate electrode and the semiconductor layer.