| abstract |
In a thin film transistor using an oxide semiconductor as an active layer, it is one of the problems to prevent changes in the composition, film quality, interface, etc. of the oxide semiconductor region forming the active layer, and to stabilize electrical characteristics of the thin film transistor. In a thin film transistor using the first oxide semiconductor region as an active layer, a second oxide semiconductor region having a lower conductivity than the first oxide semiconductor is formed between the first oxide semiconductor region and the protective insulating layer of the thin film transistor. Since it functions as a protective layer of the first oxide semiconductor region, it is possible to prevent the change of the composition of the first oxide semiconductor region and the deterioration of the film quality and to stabilize the electrical characteristics of the thin film transistor. |