A thin-film transistor device includes: a gate electrode above a substrate; a gate insulating film on the gate electrode; a crystalline silicon thin film including a channel region which is provided on the gate insulating film; semiconductor films on at least the channel region; an insulating film made of an organic material which is provided over the channel region and above the semiconductor films; a source electrode over at least an end portion of the insulating film; and a drain electrode over at least the other end portion of the insulating film and facing the source electrode. The semiconductor films include at least a first semiconductor film and a second semiconductor film provided on the first semiconductor film. A relationship ECP