The invention prevents the reduction of a display quality caused by a light leak current of a thin film transistor used in a display device. A lower metal layer is formed on a substrate, and a buffer film, a semiconductor layer, a gate insulation film, and a gate wiring are formed thereon in this order. An interlayer insulation film having contact holes is formed on the gate wiring. A source wiring and a drain wiring connected to a source and a drain of the semiconductor layer through the contact holes respectively extend onto the interlayer insulation film. The source wiring, the drain wiring, and the lower metal layer extend from contact hole side respectively to cover a region that does not extend over an end of the gate wiring in the width direction on or under the semiconductor layer and the gate wiring.