A method for fabricating through-silicon via structure includes the steps of: providing a semiconductor substrate; forming at least one semiconductor device on surface of the semiconductor substrate; forming a dielectric layer on the semiconductor device, in which the dielectric layer includes at least one via hole; forming a first conductive layer on the dielectric layer and filling the via hole; performing an etching process to form a through-silicon via in the first conductive layer, the dielectric layer, and the semiconductor substrate; depositing a second conductive layer in the through-silicon via and partially on the first conductive layer; and planarizing a portion of the second conductive layer until reaching the surface of the first conductive layer.