A thin-film transistor is provided in which the thickness of the insulating film is optimized. A gate electrode is formed on a transparent substrate. A silicon nitride film and a silicon oxide film, acting as a gate insulating film, are formed over the transparent substrate. A polycrystalline silicon film, being a semiconductor film, is formed acting as an active region. A stopper is formed on the polycrystalline silicon film corresponding to the gate electrode. A silicon oxide film and a silicon nitride film, acting as an interlayer insulating film, are deposited as to cover the stopper region. The total film thickness T1 of the stopper and the silicon oxide film is formed to be thinner than (the thickness T2 of the silicon nitride film×8000 Å)½. This structure allows hydrogen atoms to be sufficiently supplied from the silicon nitride film into the polycrystalline silicon film via the stopper and the silicon oxide film, so that crystalline defects in the polycrystalline silicon film can be filled with the hydrogen atoms.