Thanks to their unique properties and potential applications in various smart electronic devices, micro-supercapacitors have been increasingly investigated for on-chip energy storage. In this presentation, we describe our most recent attempts to increase the areal capacitance and energy of micro-supercapacitors. We deposited hydrated ruthenium oxide onto a highly porous gold current collector to realize a 3D electrode with unprecedented performances, fully compatible with current micro-fabrication and silicon-based device technology. The resulting electrode exhibits a capacitance per surface area in excess of 3 F.cm −2 , and-for the first time-an all-solid-state micro-supercapacitor with a specific energy per surface area comparable to that of lithium-ion micro-batteries has been achieved, but with superior power and cycling stability.