A semiconductor device includes an insulating substrate and a TFT element disposed on the substrate. The TFT element includes a gate electrode, a gate insulating film, a semiconductor layer, and a source electrode and a drain electrode arranged in that order on the insulating substrate. The semiconductor layer includes an active layer composed of polycrystalline semiconductor and a contact layer segment interposed between the active layer and the source electrode and another contact layer segment interposed between the active layer and the drain electrode. The source and drain electrodes each have a first face facing the opposite face of the active layer from the interface with the gate insulating layer and a second face facing an etched side face of the active layer. Each contact layer segment is disposed between the active layer and each of the first and second faces of the source or drain electrode.