| 摘要 |
PURPOSE: A method for forming a multiple gate oxide layer is provided to improve process margin by forming the multiple gate oxide layer with different thickness using an oxynitride layer. CONSTITUTION: An oxynitride layer is formed on a semiconductor substrate(31) defined by the first region, the second region and the third region. Ions for controlling oxidation speed are implanted into the first region. The oxynitride layer on the first and second region is selectively removed. The first, second and third gate oxide layer(37a,37b,37c) having different thickness each other are formed on the first, second and third region, respectively by oxidizing the substrate.
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