| 摘要 |
PURPOSE:To improve the accuracy in controlling trench width by a method wherein, when a semiconductor layer formed on a step difference on a semiconductor substrate is provided with the etching resistance, the thickness of semiconductor layer is controlled. CONSTITUTION:A trench 3 is formed in a silicon oxide film on a substrate 1 and then an oxidation proof film 4 is further formed. Firstly a polycrystalline silicon film 5 d1 thick is formed. At this time, the trench 3 becomes W2 wide. Secondly another polycrystalline silicon film 6 is left only inner sides of the trench 3 by means of RIE process and then heated for oxidation. The other oxide film 7 on the surface of film 6 may be utilized as an etching mask. The thickness d1 of film 7 is controlled by the time of oxidation. The inner side of film 7 is grown inward by 0.55 times of the thickness d2 from the inner side of film 6 before the oxidation. Resultantly the width of trench 3 may be represented by the expression W3=W1-2d1-1.1d2. The width W3 may be controlled by means of controlling the thickness d1, d2. |
