According to one embodiment, a display device includes a semiconductor layer, a first insulating film covering the semiconductor layer, a gate line extended in a first direction on the first insulating film to intersect the semiconductor layer, a second insulating film covering the gate line, a first common electrode formed on the second insulating film, a third insulating film covering the first common electrode, a source line which is extended in a second direction on the third insulating film and which is in contact with the semiconductor layer, and a fourth insulating film which covers the source line and which has a thickness greater than a thickness of the third insulating film.