A semiconductor structure includes a semiconductor device, an interconnect structure, a dielectric layer, and a redistribution layer (RDL). The interconnect structure is disposed over the semiconductor device. The dielectric layer is disposed over the interconnect structure. The RDL includes a conductive structure over the dielectric layer and a conductive via extending downwards from the conductive structure and through the dielectric layer. The conductive via includes a bottom portion, a top portion and a tapered portion between the bottom and top portions, in which the tapered portion has a width variation greater than that of the bottom and top portions.