A semiconductor device includes a first conductive element electrically connected to an interconnect structure, wherein the first conductive element includes a first conductive material. The semiconductor device further includes an RDL over the first conductive element and electrically connected to the first conductive element, wherein the RDL includes a second conductive material different from the first conductive material. The semiconductor device further includes a passivation layer over the RDL, wherein a top portion of a sidewall of the second passivation layer includes a convex curve protruding in a direction parallel to a top surface of the interconnect structure, a width of the top portion at a bottom of the convex curve is less than a width of the top portion at a middle of the convex curve, and the middle of the convex curve is above the bottom of the convex curve.