| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device which has a capacitive element constituted of an insulating film that has only a small surface unevenness and a high dielectric strength and also provide a method for manufacturing it. SOLUTION: On a thermal oxide film 2 formed on an Si substrate 1, a polycrystalline Si layer 3 of 2500Åin thickness is formed as a lower electrode of a capacitive element by the low-pressure CVD method. This substrate 1 is heat-treated with phosphorus oxychloride being used as a source gas to form an extremely thick PSG film 6 on the polycrystalline Si layer 3. By this heat-treatment, a polycrystalline Si layer 3a with grown Si grain boundaries can be obtained. After removing the PSG film 6 by etching with an HF liquid, the substrate 1 with the polycrystalline Si layer 3a is heat-treated in O2 gas at 1135 deg.C for 120 seconds by rapid lamp heating to form an insulating film 5 on the surface of the Si layer 3a. Since this heat-treatment is conducted for a very short time, the growth of the grain boundaries of Si is prevented and therefore the insulating film 5 of a surface unevenness of 80Åor below is formed by a high-temperature stress relaxation effect. In like manner, a polycrystalline Si layer 4 is formed as an upper electrode on the insulating film 5 and is patterned. After that, part of the lower electrode is exposed and the upper and the lower electrode are wired and thus a capacitive element is fabricated.
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