The purpose of the present invention is to decrease the resistance of the drain and source in the TFT of the oxide semiconductor as well as to have stable Vd-Id characteristics of the TFT. The structure of the present invention is as follows: A display device having plural pixels including thin film transistors (TFT) having oxide semiconductor films comprising: a gate insulating film formed on the oxide semiconductor film, an aluminum oxide film formed on the gate insulating film, a gate electrode formed on the aluminum oxide film, a side spacer formed on both sides of the gate electrode, and an interlayer insulating film formed on the gate electrode, the side spacer, a drain and a source, wherein in a plan view, and in a direction from the drain to the source, a length of the gate electrode is shorter than a length of the aluminum oxide film.