The mechanisms of a novel two-step metallorganic chemical vapor deposition (MOCVD) of copper thin films have been determined. In a previous study, this MOCVD method proved to succeed in forming smooth and continuous thin copper film for use in electroplating [C. Lee and H.-H. Lee, Electrochem. Solid-State Lett., 8, G5 (2005)]. The current study tested the feasibility of condensing the two steps into one, but unexpectedly discovered an interesting phenomenon. Consequently, the mechanisms of the two-step MOCVD of Cu films have become clear. The determination of detailed mechanisms of this MOCVD method can further establish its status as a replacement for sputtering in the deposition of seed layers for electroplating. (c) 2005 The Electrochemical Society.