The continuous increase of small electronic devices calls for small energy storage components, commonly known as micro-supercapacitors, that can ensure autonomous operation of these devices. In this work, we propose a simple and straightforward method to achieve high energy and power densities of a silicon-based micro-supercapacitor, consisting of silicon nanowires decorated with ruthenium nanoparticles (Ru/Si NWs). The Si NWs are obtained through the common vapor-liquid-solid (VLS) growth mechanism, while a simple electroless process is used to deposit Ru nanoparticles. While silicon nanostructuration allows to increase the surface area, coating with Ru NPs introduces a pseudocapacitance necessary to attain high energy and power densities. The Ru/Si NWs micro-supercapacitor exhibits a specific capacitance of 36.25 mF cm(-2) at a current density of 1 mA cm(-2) in a neutral Na2SO4 electrolyte and a high stability over 25 000 cycles under galvanostatic charge-discharge at 1 mA cm(-2). A solid state supercapacitor is then fabricated with symmetric electrodes separated by a polyvinyl alcohol/sulfuric acid electrolyte. The device displays a specific capacitance of similar to 18 mF cm(-2) at a current density of 1 mA cm(-2) and a specific power density 0.5 mW cm(-2). This solid-state nanowire device also exhibits a good stability over 10 000 galvanostatic charge-discharge cycles. (C) 2019 Elsevier Ltd. All rights reserved.