A semiconductive counter electrode covers a highly electronically conductive electric current buss. The semiconductive counter electrode is impervious to ion flow. A substrate holder is operable to hold a substrate and to form a thin fluid gap between the semiconductive counter electrode and a substrate surface. A thin liquid electrolyte layer is located in the thin fluid gap. A power supply connected to the electric current buss and a peripheral edge of a conductive substrate surface is able to generate a potential difference between the electric current buss and the semiconductive counter electrode, on one side of the electrolyte layer, and the substrate on the other side. The semiconductive counter electrode provides a substantial resistance in the various current flow paths between the electric current buss and the semiconductive counter electrode, on one side, and the conductive substrate surface, on the other, thereby enhancing control of current distribution.