This paper introduces a silicon three-dimensional (3D) micro supercapacitor, featured by using self-supporting nano porous composite materials and interdigital electrodes with high-aspect-ratio. A way to prepare self-supporting materials has been developed, and composites that contain an activated carbon as the active component have been studied and designed to meet the requirements for adequate specific capacitance, good conductivity and strong structure. By combining the designed composite with microfabrication techniques, a micro supercapacitor with high-aspect-ratio interdigital electrodes has been achieved. Electrochemical characterization results of the prototype with NaNO3 electrolyte demonstrate that the 3D supercapacitor exhibits an outstanding overall performance. A large capacitance of 90.7mFcm−2 and a fast power of 51.5mWcm−2 are calculated. Robust stability and high charge/discharge efficiency are also observed. Moreover, this study provides a scalable device built by compatible fabrication method, which is applicable to the integration of high-performance supercapacitors on chip.