A wafer-level stack package includes semiconductor chips, first connection members, a second connection member, a substrate and an external connection terminal. The semiconductor chips have a power/ground pad and a signal pad. The first connection members are electrically connected to the power/ground pad and the signal pad of each of the semiconductor chips. The second connection member is electrically connected to at least one of the power/ground pads of each of the semiconductor chips, the power/ground pads being connected to the first connection members. The substrate supports the stacked semiconductor chips, the substrate including wirings that are electrically connected to the first connection members and the second connection member. The external connection terminal is provided on a surface of the substrate opposite to a surface where the semiconductor chips are stacked, wherein the external connection terminals are electrically connected to the wirings, respectively.