The invention provides a film transistor and a source matrix substrate with the film transistor and the display device. The invention improves the electric current driving capability of a thin film transistor without the yield being decreased due to a defective leak between a source electrode/drain electrode and a gate electrode or due to a decrease in an off-characteristic. A thin film transistor according to the present invention includes a gate electrode; an insulating film covering the gate electrode; a semiconductor layer provided on the insulating film; and a source electrode and a drain electrode provided on the insulating film and the semiconductor layer. The insulating film is a multiple layer insulating film including a first insulating layer and a second insulating layer provided on the first insulating layer. The multiple layer insulating film has a low stacking region excluding the first insulating layer and a high stacking region in which the first insulating layer and the second insulating layer are stacked. The first insulating layer is provided so as to cover at least an edge of the gate electrode. The semiconductor layer is provided on both the low stacking region and the high stacking region of the multiple layer insulating film. The semiconductor layer and the low stacking region are arranged such that a path of a current flowing between the source electrode and the drain electrode necessarily passes a part of the semiconductor layer which is located above the low stacking region.