A stacked structure of a spiral inductor includes a first metal layer, a second metal layer, a first set of vias, and a second set of vias. The first metal layer includes a first segment, a second segment, and a third segment, wherein the layout direction of the third segment is different from the layout direction of the first and second segments. The second metal layer includes a fourth segment, a fifth segment, and a sixth segment connected to the fifth segment, wherein the layout direction of the sixth segment is different from the layout direction of the fourth and fifth segments. The first set of vias connects the first and fourth segments, and they construct a first shunt winding. The second set of vias connects the second and fifth segments, and they construct a second shunt winding. The third and sixth segments construct a crossover region.