A thin film transistor includes: a gate electrode; a gate insulating layer above the gate electrode; an oxide semiconductor layer disposed above the gate insulating layer; and a source electrode and a drain electrode disposed above the oxide semiconductor layer and electrically connected to the oxide semiconductor layer, wherein metallic elements included in the oxide semiconductor layer include at least indium (In), fluorine is included in a region which is an internal region in the oxide semiconductor layer and is close to the gate insulating layer, and a fluorine concentration of the region close to the gate insulating layer in the oxide semiconductor layer is higher than a fluorine of a contact region for the source electrode or the drain electrode in the oxide semiconductor layer.
