| 摘要 |
PURPOSE:To provide a fine element separating region by utilizing that, when an Si3N4 film is used as a mask, an SiO2 film is intruded to the edge bottom of the Si3N4 film to reduce a nonoxidative region smaller than the mask. CONSTITUTION:An SiO2 film 22, a polysilicon film 23, a polysilicon film 24, a polysilicon film 25 and an Si3N4 film 26 are laminated on a P-type Si substrate 21. The film 26 is opened with a resist mask 27 to form an SiO2 film 28, the films 25, 26 are removed, the film 24 is subjected to an RIE method, and the film 28 is removed. At this time, the window size L13 of the mask 14 is formed in a relation of L11>L12>L13. When a field oxide film 29 is formed with the mask 24, the size L14 of the film 29 becomes larger than the L13. A MOSFET is formed then as the normal method. According to this configuration, an element separating region is reduced to improve the integration.
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