There is provided a method for manufacturing a flexible semiconductor device. The method of the present invention comprises the steps of: (A) providing a metal foil; (B) forming an insulating layer on the metal foil, the insulating layer having a portion serving as a gate insulating film; (C) forming a supporting substrate on the insulating layer; (D) etching away a part of the metal foil to form a source electrode and a drain electrode therefrom; (E) forming a semiconductor layer in a clearance portion located between the source electrode and the drain electrode by making use of the source and drain electrodes as a bank member; and (F) forming a resin film layer over the insulating layer such that the resin film layer covers the semiconductor layer, the source electrode and the drain electrode. In the step (F), a part of the resin film layer interfits with the clearance portion located between the source and drain electrodes.