A semiconductor device includes a semiconductor substrate, a copper-containing metal interconnect over the semiconductor substrate, and a copper-containing connection plug, and the metal interconnect includes metal elements other than copper, and a concentration of different metal elements in a connection portion between the metal interconnect and the connection plug is higher than a concentration of the different metal elements in a center portion of the metal interconnect, and higher than a concentration of different elements in upper face portion of the metal interconnect other than the connection portion.