A semiconductor device includes a substrate having a top surface and a bottom surface, and a through-silicon via (TSV) extending from the top surface of the substrate to the bottom surface of the substrate, the TSV having a height and a side profile extending along a longitudinal axis, wherein the side profile has an upper segment forming a first angle relative to the longitudinal axis, and a lower segment forming a second angle relative to the longitudinal axis, the second angle being different from the first angle, and wherein the lower segment has a height that is less than 20% of the height of the TSV.