| 摘要 |
PURPOSE:To integrate capacity of an MOS device by a method wherein the semiconductor regions having impurity concentration being different by two figures or more mutually are thermally oxidized to provide oxide films having different thickness mutually. CONSTITUTION:The diffusion coefficient of O2 when the thermal oxide film is to be formed depends on concentration of impurities of a substrate to be oxidized, and the larger concentration is, the thicker the film becomes. A P type layer 13 and an N<+> type layer 14 having impurity concentration being larger by two figures or more are formed selectively on an N type epitaxial layer 12 on a P type Si substrate 11, and when it is treated in the dry O2 atmosphere at 900 deg.C for about 60min, an SiO2 film is made to grow on the N<+> type layer being thicker than the film grown on the P type layer. Electrode openings are formed in the P type layer 13 and the N<+> type layer 14, and upper part electrodes 17, 19 and lower part electrode lead out layers 18, 20 consisting of Al are provided. By this constitution, capacitors of two kind or more having different capacity value per unit area can be formed at the same time on one chip without changing the manufacturing process, and integration of capacity can be attained. |
