A display device including a substrate having thin film transistors (TFT) comprising: the TFT including an oxide semiconductor film, a gate electrode and an insulating film formed between the oxide semiconductor film and the gate electrode, wherein a first aluminum oxide film and a second aluminum oxide film, which is formed on the first aluminum oxide film, are formed between the insulating film and the gate electrode, an oxygen concentration in the first aluminum oxide film is bigger than an oxygen concentration in the second aluminum oxide film.