An insulating film (23) of a higher dielectric constant than silicon dioxide, for example of tantalum oxide, is formed on a p-type substrate (21). The insulating film (23) contains an n-type impurity, for example phosphorus. An electrode (24), for example of molybdenum silicide, is formed on the insulating film (23). By a heat treatment carried out for example for 30 minutes at a temperature of 1000°C an n-type region (25) is formed in the p-type substrate (21) by diffusion of impurity (phosphorus) from the insulating film (23), into the surface of the substrate (21).
Thereby an MIS type capacitor can be provided in which the insulating film (23) has a higher dielectric constant than silicon dioxide, whereby an increased amount of electric charge can be held in a capacitor of the same size as one in which an insulating film is provided of silicon dioxide. By the provision of the n-type inversion region (25) the capacitor can be charged up to the voltage of the power source connected to the electrode (24). By the diffusion of impurities from the insulating film (23) into the substrate (21) to form the region (25), the region (25) is formed in an accurate self-aligning fashion.