Patent ID: 8916868

Claim:
A semiconductor device comprising: a first transistor comprising: a first channel formation region including a semiconductor material; and a first gate electrode overlapping with the first channel formation region, an insulating layer with a trench covering the first transistor, wherein part of the first gate electrode is exposed without being covered with the insulating layer; and a second transistor comprising: an oxide semiconductor film including a second channel formation region; a source electrode layer and a drain electrode layer over the insulating layer and the oxide semiconductor film, wherein each of the source electrode layer and the drain electrode layer comprises a metal layer; a gate insulating layer over the oxide semiconductor film, the source electrode layer, and the drain electrode layer; and a second gate electrode layer over the gate insulating layer, wherein the trench includes a lower end corner portion having a curved shape and an upper end corner portion having a curved shape, wherein the second channel formation region is in contact with a bottom surface, an inner wall surface, the lower end corner portion, and the upper end corner portion of the trench, wherein the oxide semiconductor film contains indium, wherein the oxide semiconductor film includes crystals which contain indium and whose c-axes are aligned substantially perpendicular to a surface of the oxide semiconductor film at least in a region overlapping with the upper end corner portion, wherein the upper end corner portion has a curvature radius of longer than or equal to 20 nm and shorter than or equal to 60 nm, wherein the lower end corner portion has a curvature radius of longer than or equal to 20 nm and shorter than or equal to 60 nm, and wherein one of the source electrode layer and the drain electrode layer of the second transistor is in direct contact with the part of the first gate electrode.