| 摘要 |
PURPOSE:To have a film self-alignedly formed precisely on a plane of a certain type of material or extending but a little out of said plane by a method wherein an etching method is applied whose etching rate varies dependent upon the quantity of impurity contained in a third material wherein impurity concentration is locally varied. CONSTITUTION:A silicon oxide film 2 is formed on a silicon substrate 1 and, on the silicon oxide film 2, a pattern of a silicon nitride film 3 is formed. Boron 4 is then driven into the surface. Next, on the surface, a film 5 is formed, composed of polycrystalline silicon or amorphous silicon. A thermal treatment process follows, wherein the boron concentration in a silicon material 6 on the silicon oxide film 2 will be far higher than that in a silicon material 7, with the boron diffusion factor being greater in the silicon oxide film 2 than in the silicon nitride film 3. Finally, the silicon substrate 1 is subjected to etching in a water solution of caustic potash. In this process, with the silicon material 7 containing a low concentration of boron being affected by etching more rapidly than the silicon material 6 containing a high concentration of boron, almost all of the silicon materials 6 will remain even after the silicon material 7 has been totally removed by etching.
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