A Cu alloy for semiconductor interconnections contains at least one selected from the group consisting of 0.10 to 10 atomic percent of Sb, 0.010 to 1.0 atomic percent of Bi, and 0.01 to 3 atomic percent of Dy, with the balance being Cu and inevitable impurities. The Cu alloy can be reliably embedded in narrow trenches and/or via holes for interconnections.