MANUFACTURE OF MOS TRANSISTOR

PURPOSE:To make only the interface between a silicon oxide film and an electrode above it and the silicon oxide film in the vicinity of the interface contain chromium, and also, prevent the chromium from having adverse effects on the distribution of concentration of the impurities within a silicon substrate. CONSTITUTION:A silicon oxide film 14 containing chromium only in the vicinity of the surface of the silicon oxide film 12 by diffusing the chromium into the silicon oxide film 12 by performing heat treatment after applying nitric acid solution containing chromium ingredients on the surface of the silicon oxide film 12 made on a silicon substrate 11. Accordingly, a MOS transistor, where there is practically no deterioration of the insulation property of the silicon film by making the silicon oxide film contain chromium effectively, and besides the deterioration of the electric property in the silicon substrate scarcely occurs, and the threshold voltage can be controlled, can be manufactured easily.