A thin film transistor comprising: a substrate; a gate electrode on the substrate; a gate insulation film on the gate electrode; an oxide semiconductor layer on the gate insulation film; a channel protection film on the oxide semiconductor layer; source and drain electrodes on the channel protection film; and a passivation film on the source and drain electrodes, wherein, (a) each of the gate insulation film, and passivation film comprises a laminated structure and includes a first layer made of aluminum oxide and a second layer made of an insulation material including silicon, and (b) the passivation film covers edges of the oxide semiconductor layer. The transistor is capable of suppressing desorption of oxygen and from the oxide semiconductor layer and reducing the time for film formation thereof.