Provided is an in-wiring-layer active element (component) which allows for electrical isolation between a gate electrode and a channel in a top gate structure. A semiconductor device includes a first wiring layer, a second wiring layer, and a semiconductor element. The first wiring layer has a first interlayer insulating layer, and a first wire embedded in the first interlayer insulating layer. The second wiring layer has a second interlayer insulating layer, and second wires embedded in the second interlayer insulating layer. The semiconductor element is provided at least in the second wiring layer. The semiconductor element includes a semiconductor layer provided in the second wiring layer, a gate insulating film provided in contact with the semiconductor layer, a gate electrode provided on the opposite side of the semiconductor layer via the first gate insulating film, and a first side wall film provided over a side surface of the semiconductor layer.