A through-silicon via and a method for forming the same are provided. The method includes: providing a semiconductor substrate, the semiconductor substrate including an upper surface and an opposite lower surface; etching the upper surface of the semiconductor substrate to form an opening; filling the opening with a conductive material to form a first nail; etching the lower surface of the semiconductor substrate to form a recess, such that the first nail is exposed at a bottom of the recess; filling the recess with a conductive material that can be etched, and etching the conductive material that can be etched to form a second nail, such that the second nail is vertically connected with the first nail; and filling a gap between the second nail and the semiconductor substrate and a gap between the second nail and an adjacent second nail with a dielectric layer. Then invention can improve the reliability of through-silicon vias and avoid voids.