Disclosed is a thin film transistor that includes a gate electrode, a semiconductor overlapping with the gate electrode, a source electrode that is electrically connected to the semiconductor, a drain electrode that is electrically connected to the semiconductor and faces the source electrode, and a stacked gate insulating layer that is positioned between the gate electrode and semiconductor. The stacked gate insulating layer includes an aluminum oxide layer. A method of manufacturing the same and a display device including the thin film transistor are also disclosed.