Superconformal Au deposition is demonstrated in a Na3Au(SO3)(2) based electrolyte that exhibits critical behavior with addition of the deposition-rate suppressing additive polyethyleneimine (PEI). The critical behavior results from s-shaped negative differential resistance that is stabilized by the resistive electrolyte as evident in hysteretic cyclic-voltammetry. Specifically, the hysteretic potential range indicates conditions under which two states can exist: one in which adsorbed PEI suppresses gold deposition and the other in which ongoing gold deposition continues to disrupt and bury arriving suppressor. The specimen history determines the state observed. "Extreme" bottom-up filling of Through Silicon Vias (TSVs) and superconformal filling of submicrometer Damascene trenches are demonstrated and explained in this context. (C) 2013 The Electrochemical Society. All rights reserved.