A semiconductor device having interconnects is reduced in leakage current between the interconnects and improved in the TDDB characteristic. It includes an insulating interlayer 108, and interconnects 160 filled in grooves formed in the insulating interlayer, including a copper layer 124 mainly composed of copper, having the thickness smaller than the depth of the grooves, and a low-expansion metal layer 140, which is a metal layer having a heat expansion coefficient smaller than that of the copper layer, formed on the copper layer.