According to one embodiment, a method of manufacturing a thin-film transistor circuit substrate including forming an oxide semiconductor thin film above an insulative substrate, forming a gate insulation film and a gate electrode which are stacked on a first region of the oxide semiconductor thin film, and exposing from the gate insulation film a second region and a third region of the oxide semiconductor thin film, the second region and the third region being located on both sides of the first region of the oxide semiconductor thin film, forming an interlayer insulation film of silicon nitride including dangling bonds of silicon, the interlayer insulation film covering the second region and the third region of the oxide semiconductor thin film, the gate insulation film and the gate electrode, and forming a source electrode and a drain electrode.