A transistor formed on a semiconductor substrate has a gate electrode formed via a gate insulating film and first and second diffusion layers formed in the semiconductor substrate, the first and second diffusion layers being positioned at both sides of the gate electrode. A first electrode is connected to the first diffusion layer of the transistor. A capacitor insulating film formed on the first electrode is formed of a silicon oxide film containing a substrate which is faster than Cu in diffusion velocity and which more readily reacts with oxygen than Cu does. A second electrode formed on the capacitor insulating film is formed of one of a Cu layer and another Cu layer containing the substance.