A semiconductor device includes a substrate, a first dielectric layer, a second dielectric layer, and a third dielectric layer. The first dielectric layer is disposed on the substrate, around a first metal interconnection. The second dielectric layer is disposed on the first dielectric layer, around a via and a second metal interconnection. The second metal interconnection directly contacts the first metal interconnection. The third dielectric layer is disposed on the second dielectric layer, around a first magnetic tunneling junction (MTJ) structure and a third metal interconnection. The third metal interconnection directly contacts top surfaces of the first MTJ structure and the second metal interconnection, and the first MTJ structure directly contacts the via.