A method of forming a thin film interconnect in which a film is formed by sputtering method using a Cu—Ca alloy target and a thin film interconnect formed by the method, the method comprising: forming a Cu—Ca alloy film by sputtering method using a Cu—Ca alloy target that contains 0.5 atomic % or more and less than 5 atomic % of Ca, and the balance consisting of Cu and unavoidable impurities; and performing heat treatment of the Cu—Ca alloy film at a temperature of 300 to 700° C. in an inert gas atmosphere containing trace amount of oxygen defined by oxygen partial pressure in the range of 10−4 to 10−10 atm.