Abstract: Copper-containing thin films can be industrially advantageously formed by chemical vapor deposition using as the copper source a divalent copper complex bearing ?-diketonato ligands having silyl ether linkage. A representative example of the divalent copper complex is represented by the formula (I): wherein Z is hydrogen or alkyl; X is a group represented by the formula (I-I), in which Ra is alkylene, and each of Rb, Rc and Rd is alkyl; and Y is an alkyl group or a group represented by the formula (I-I), in which Ra is alkylene, and each of Rb, Rc and Rd is alkyl.