| 摘要 |
PURPOSE: A method for forming a gate oxide layer having a double structure is to prevent a boron ion implanted into an upper polysilicon layer from being diffused into the bottom through a gate insulating layer by forming a nitride oxide layer having the double structure. CONSTITUTION: The first nitride oxide layer(15) is deposited on a semiconductor substrate under the atmosphere of an NO gas. An oxide layer(20) is deposited on the entire surface of the semiconductor substrate under the atmosphere of an oxygen gas. Thereby, the concentration of nitrogen is distributed within the first nitride oxide layer. The second nitride oxide layer(25) is deposited on the oxide layer under the atmosphere of the NO gas. As result, a gate insulating layer(30) is formed. The gate insulating layer consists of the first nitride oxide layer, the oxide layer, and the second nitride oxide layer. And the boron ions are diffused into the semiconductor substrate by the first and second nitride oxide layers.
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