| abstract |
A semiconductor device using an oxide semiconductor, in which miniaturization is achieved while maintaining good electrical characteristics. In a transistor including an oxide semiconductor layer, a gate insulating layer in contact with the oxide semiconductor layer, and a gate electrode layer overlapping with the oxide semiconductor layer through the gate insulating layer, an upper surface of the gate insulating layer and the gate electrode layer An insulating layer having a lower permeability to oxygen than that of the gate insulating layer is provided in contact with the side surface. In the insulating layer, the thickness of the region in contact with the upper surface of the gate insulating layer is larger than the thickness of the region in contact with the side surface of the gate electrode layer. [Selection] Figure 1 |