A semiconductor device includes a semiconductor substrate, a metal layer, a dielectric layer, and a via. The metal layer is disposed above the semiconductor substrate. The dielectric layer is disposed between the metal layer and the semiconductor substrate. The via is embedded in the dielectric layer and comprises a first portion and a second portion between the first portion and the semiconductor substrate. The first portion of the via has a first width. The second portion of the via has a second width greater than the first width of the first portion.