There is provided a bottom gate channel etched thin film transistor that can suppress initial Vth depletion and a Vth shift. A thin film transistor is formed, including a gate electrode interconnection disposed on a substrate, a gate insulating film, an oxide semiconductor layer to be a channel layer, a stacked film of a source electrode interconnection and a first hard mask layer, a stacked film of a drain electrode interconnection and a second hard mask layer, and a protective insulating film.