| 摘要 |
PURPOSE:To form a thick insulating film for element isolation by a method wherein an oxide film formed by oxidizing a polycrystalline silicon layer is laminated on a thick oxide film formed by using a non-oxidizable film as a mask. CONSTITUTION:A silicon substrate 11 is oxidized to form a silicon nitride film 12 and then a silicon nitride film 13 is depositionformed. Next, after selectively removing the silicon nitride film 13, ion is implanted to form an inversion preventive layer 11A further forming an element isolating oxide film 14. Later, a polycrystalline silicon layer 15 is vapor-grown on the silicon nitride film 13 and the element isolating oxide film 14. Then, overall polycrystalline silicon layer 15 is oxidized to form an oxide film 15A which is immersed in ammonium fluoride solution to be removed until the surface of silicon nitride film 13 is exposed. Through these procedures, the oxide film 15A is left on the element isolating oxide film 14 so that the silicon nitride film 13 may be removed by chemical dry etching process to form a thick element isolating oxide film 16.
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