This paper demonstrates superconformal electrodeposition of copper in trenches using a two-step process. The substrate is first derivitized with a submonolayer coverage of catalyst and then transferred for electroplating in a cupric sulfate electrolyte containing an inhibitor. For an optimum catalyst coverage, superconformal, "bottom-up'' filling of trenches and vias is observed. If the catalyst coverage is too low or too high, conformal or subconformal deposition occurs, resulting in void formation during feature filling. The filling behavior of the derivitized electrodes is analogous to that obtained using a single (conventional) electrolyte containing both catalytic and inhibiting species. Restricting the catalyst to the surface by derivitization prior to metal deposition provides strong support for the curvature-enhanced accelerator coverage mechanism of superconformal film growth. From a technical perspective, the two-step process offers an interesting solution to the difficult control issues associated with catalyst destruction and related aging effects known to occur in the "conventional'' single-electrolyte superfilling process. (C) 2002 The Electrochemical Society.