The purpose of the present invention is to realize the TFT of the oxide semiconductor having a superior characteristics and high reliability during the product's life. The structure of the present invention is as follows. A display device comprising: a substrate including a display area where plural pixels are formed, the pixel includes a first TFT of a first oxide semiconductor, a first gate insulating film is formed on the first oxide semiconductor, the first gate insulating film is a laminated film of a first silicon oxide film and a first aluminum oxide film, a gate electrode is formed on the first aluminum film.