To provide a display device including a thin film transistor in which high electric characteristics and reduction in off-current can be achieved. The display device having a thin film transistor includes a substrate, a gate electrode provided over the substrate, a gate insulating film provided over the gate electrode, a microcrystalline semiconductor film provided over the gate electrode with the gate insulating film interposed therebetween, a channel protection layer which is provided over and in contact with the microcrystalline semiconductor film, an amorphous semiconductor film provided over the gate insulating film and on a side surface of the microcrystalline semiconductor film and the channel protection layer, an impurity semiconductor layer provided over the amorphous semiconductor film, and a source electrode and a drain electrode provided over and in contact with the impurity semiconductor layer. The thickness of the amorphous semiconductor film is larger than that of the microcrystalline semiconductor film.