Disclosed herein is a method of forming a semiconductor structure. The method includes the steps of: forming a first dielectric layer having a first through hole on a precursor substrate, in which the first through hole passes through the first dielectric layer; filling a sacrificial material in the first through hole; forming a second dielectric layer having a second through hole over the first dielectric layer, in which the second through hole exposes the sacrificial material in the first through hole, and the second through hole has a bottom width less than a top width of the first through hole; removing the sacrificial material after forming the second dielectric layer having the second through hole; forming a barrier layer lining sidewalls of the first and second through holes; and forming a conductive material in the first and second through holes.