| abstract |
(57) [Summary] In a thin film transistor having a dual gate structure, carriers are likely to be generated at an interface between a semiconductor layer and an insulating film, and carriers are injected into the insulating film or an interface between the insulating film and the semiconductor layer. There is a problem that the threshold value rises. In a thin film transistor having a dual gate structure, a lower region of a channel formation region of the semiconductor film in contact with the first gate insulating film and an upper region of the thin film transistor in contact with the second gate insulating film are provided. , An impurity element imparting a conductivity type different from the conductivity type of the source region and the drain region is included, and a region between the upper region and the lower region is intrinsic or has a concentration of 1 × 10 15 / cm 3 or less. A thin film transistor including an impurity element imparting the same conductivity type as a region and a lower region is provided. |