there is presented a semiconductor device including multiple levels of copper interconnects ; wherein the surface of a copper interconnect corresponding to at least one underlying layer of another copper interconnect layer is turned into copper oxide to a thickness of 30 nm or more by oxidation conducted at the oxidation rate of 20 nm / min or less , and thereby the reflection of the exposure light from the lower - level copper interconnect is prevented , in forming by means of photolithography a trench to form a copper interconnect through damascening .