A semiconductor device may include a semiconductor substrate, a conductive pad on the semiconductor substrate, a passivation layer overlying the semiconductor substrate and exposing the conductive pad, and a bump structure. The bump structure may include a first bump structure on the conductive pad and a second bump structure on the passivation layer. The first bump structure may include a base bump layer, a first pillar bump layer, and a first solder bump layer that are sequentially stacked on the conductive pad. The second bump structure may include a second pillar bump layer and a second solder bump layer that are sequentially stacked on the passivation layer.