Provided is a semiconductor device including a transistor with large on-state current even when it is miniaturized. The transistor includes a pair of first conductive films over an insulating surface; a semiconductor film over the pair of first conductive films; a pair of second conductive films, with one of the pair of second conductive films and the other of the pair of second conductive films being connected to one of the pair of first conductive films and the other of the pair of first conductive films, respectively; an insulating film over the semiconductor film; and a third conductive film provided in a position overlapping with the semiconductor film over the insulating film. Further, over the semiconductor film, the third conductive film is interposed between the pair of second conductive films and away from the pair of second conductive films.