A seal ring structure is formed through a multilayer structure of a plurality of dielectric films in a peripheral part of a chip region to surround the chip region. A dual damascene interconnect in which an interconnect and a plug connected to the interconnect are integrated is formed in at least one of the dielectric films in the chip region. Part of the seal ring structure formed in the dielectric film in which the dual damascene interconnect is formed is continuous. A protection film formed on the multilayer structure has an opening on the seal ring. A cap layer connected to the seal ring is formed in the opening.