JPS57177542A - Manufacturing method for semiconductor device - Google Patents

Abstract

PURPOSE:To ensure high integration by a method wherein field oxide film intrusion is effectively suppressed through selective oxidation by using as a mask a lamination of a thin Si3N4 film and a thick protective film. CONSTITUTION:A p layer 6 is provided on the surface of an n type Si substrate 1 and piled successively thereon are an SiO2 thin film 7, an Si3N4 thin film 8, and a P added polycrystalline Si thick film 9. The lower limit of the Si3N4 film 8 is determined with the thickness of the polycrystalline Si film 9 set anywhere between 2,000 and 3,000Angstrom . With the film 8 thickness not less than 700Angstrom , bird's beak intrusion advances. The intrusion quantity is extremely small when an anti- oxidation masks 10 and 11 are produced by plasma etching and a field oxide film 12 by oxidation in moisture, and the films 9a and 9b change into PSG. When the films 9 and 8 are subjected to etching, the reacting speed of the film 9 is so great that the film 9 is completely etched away without affecting the oxide film 12. A gate oxide film 13 and a polycrystalline Si film 14 are successively laid for the completion of a CMOSFET on a single substrate by the conventional technique. Intrusion by a bird's beak is thereby reduced and high integration is ensured.