| 摘要 |
PURPOSE:To prevent a steep silicon step difference from being made even if silicon is etched using alkali water solution for abating any high-frequency noise by a method wherein a boron high concentration layer having concentration gradient in the lateral direction is arranged in the part near the ends of opening surface of a gate region to be surface-processed. CONSTITUTION:A thick oxide film 16 for reducing MOS capacity is formed and then etched to make an opening part 17 so that the opening surface 17b may become at least a part of substrate main surface of a high concentration diffused layer 15 (including a region having boron concentration gradient in the lateral direction) and the substrate main surface of prospective gate formation region. The opening peripheral parts of oxide film 16 are e.g. isotropically etched to be inclined for leading-out a gate electrode. Later, the opening surface 17b is processed by silicon etching using water solution of sodium hydroxide (NaOH). Even if the gate region is surface-processed using alkali water solution, any steep silicon step difference is not made in the part near the peripheral parts on the boron high concentration diffused layer. Through these procedures, any high-frequency noise can be abated.
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