To provide a crystalline oxide semiconductor which can be used as a semiconductor of a transistor or the like. The crystalline oxide semiconductor is an oxide over a surface and includes a plurality of flat-plate-like In—Ga—Zn oxides. Each of the plurality of flat-plate-like In—Ga—Zn oxides has a crystal structure and includes a first layer, a second layer, and a third layer. The first layer includes a gallium atom, a zinc atom, and an oxygen atom. The second layer includes an indium atom and an oxygen atom. The third layer includes a gallium atom, a zinc atom, and an oxygen atom. A flat plane of each of the plurality of flat-plate-like In—Ga—Zn oxides is substantially perpendicular to a normal vector of the surface.