Patent attributes
An object is to provide a semiconductor device having a novel structure in which a transistor including an oxide semiconductor and a transistor including a semiconductor material other than an oxide semiconductor are stacked. The semiconductor device includes a first transistor, an insulating layer over the first transistor, and a second transistor over the insulating layer. In the semiconductor device, the first transistor includes a first channel formation region, the second transistor includes a second channel formation region, the first channel formation region includes a semiconductor material different from a semiconductor material of the second channel formation region, and the insulating layer includes a surface whose root-mean-square surface roughness is less than or equal to 1 nm.