Disclosed is a solid electrolyte capacitor comprising a positive electrode substrate composed of a metal having a valve action, and a dielectric oxide film, a semiconductor layer and an electroconductive layer, which are formed in order on the positive electrode substrate, wherein the electroconductive layer is a layer of a paste composed mainly of a metal oxide powder, a metal powder and an optional metal salt powder. This capacitor has a good and durable stability at a high temperature. In the process for the preparation of this capacitor, preferably the semiconductor layer formed on the dielectric oxide film is subjected to ultrasonic washing. |