A capacitor based on an electrochemically etched macroporous silicon substrate and a layered dielectric (ONO) is presented. This solid-state technology allows us to realize values of specific capacitance which so far could only be reached by electrolytic capacitors. The dependence of the capacitance on temperature, frequency, applied bias and time of operation is found to be negligible. Due to a low series resistance and a operating temperature of at least 200 degrees C the device withstands high a.c. currents. Being a silicon chip, the capacitor is fully compatible with today’s surface mounted device and multi-chip module technologies.