An I/O pad structure in an integrated circuit (IC) comprises a first vertical region in the IC including a top metal layer and one or more semiconductor devices formed thereunder, the top metal layer in the first vertical region serving as a first pad, the semiconductor devices being electrically connected to the first pad, and a second vertical region in the IC next to the first vertical region including the top metal layer and one or more through-silicon-vias (TSVs) formed thereunder, the top metal layer in the second vertical region serving as a second pad, and no semiconductor devices being formed beneath the second pad, the TSVs being electrically connected to the second pad, wherein the first and the second pad are electrically connected through at least one metal layer.