| 摘要 |
PURPOSE:To prevent a gate from being damaged due to an electric stress by making smaller the reverse withstanding voltage of a P-N junction formed between a second conductivity type diffused layer and a substrate than a voltage applied to a gate electrode for damaging the insulation of a gate insulating film. CONSTITUTION:<11>B<+> is ion implanted from a contacting hole 29 to form a P<+> type diffused layer 30 in a substrate 21 under an N<+> type diffused layer 26. The impurity density of the layer 30 is so set that the reverse withstanding voltage between the layer 26 and the layer 30 is smaller than a voltage applied to a gate electrode for damaging the gate. As a result, when a polycrystalline Si film pattern 31 is charged up in an ion implanting step or a reactive ion etching step after the ion implanting step or a high voltage is applied to the layer 26, the layer 26 - the layer 30 become a protecting diode, and the breakdown of the P-N junction occurs earlier. Accordingly it can prevent a gate oxide film 23 from being damaged.
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