The present invention provides a method by which molecules in an organic semiconductor layer can be oriented so as to make molecules in an organic semiconductor layer be oriented without damaging the organic semiconductor layer by rubbing and by which molecules in an organic semiconductor layer are oriented without losing the planarity of an interface between a gate insulating film and an organic semiconductor layer by rubbing the gate insulating film, in manufacturing an organic semiconductor having molecular orientation. One feature of the invention is that molecules in an organic semiconductor layer are highly oriented by providing a second substrate provided with an orientation film to a first substrate having a gate electrode, a gate insulator layer, a source electrode, a drain electrode, and an organic semiconductor layer so that the orientation film is in contact with the organic semiconductor layer, then applying heat, or rapidly or slowly cooling after applying heat, in manufacturing a semiconductor device.