This semiconductor device includes a substrate and a thin film transistor supported on the substrate. The thin film transistor includes a gate electrode, a semiconductor layer, a gate-insulating layer provided between the gate electrode and the semiconductor layer, and a source electrode and a drain electrode respectively making contact with the semiconductor layer. The source electrode and the drain electrode respectively include a main layer containing aluminum or copper, a lower layer having a first layer containing refractory metal and positioned at a substrate side of the main layer, and an upper layer having a second layer containing refractory metal. The upper layer is provided so as to cover an upper surface of the main layer and at least the section of the side face of the main layer that overlaps the semiconductor layer.