A manufacturing method of a
thin film transistor having at least a gate
electrode, a gate insulation film, an
oxide semiconductor layer, a first insulation film, a source
electrode, a drain
electrode, and a second insulation film on a substrate, including: forming the gate electrode on the substrate; forming the gate insulation film on the gate electrode; forming a
semiconductor layer including
amorphous oxide on the gate insulation film; patterning the gate insulation film; patterning the
oxide semiconductor layer; reducing the
oxide semiconductor layer in resistance by forming the first insulation film on the
oxide semiconductor layer in the
atmosphere not including an oxidized gas; patterning the first insulation film and forming a
contact hole between the source electrode and the drain electrode and the
oxide semiconductor layer; forming a source electrode layer and a drain electrode layer in the
oxide semiconductor layer through the
contact hole; forming the source electrode and the drain electrode through the
contact hole and allowing the first insulation film to be exposed; patterning the exposed first insulation film and allowing a channel region of the oxide semiconductor layer to be exposed; and increasing the channel region in resistance by forming the second insulation film on the surface including the channel region of the oxide semiconductor layer in the
atmosphere including an oxidized gas.