| 摘要 |
PROBLEM TO BE SOLVED: To optimize both low-voltage MOS transistor and high-voltage MOS transistor, and to increase a hot carrier withstand voltage. SOLUTION: In the low-voltage MOS transistor, a silicon oxide film 6 of 50 to 200Åis employed as a gate insulating film. In the high-voltage MOS transistor, a silicon oxide film 4 of 50 to 200Åis employed as a gate insulating film. An LDD(Lightly Doped Drain) structure is obtained by burying a source/ drain in a three-layered ONO film composing of the silicon oxide film 4 of 50 to 200Å, the silicon oxide film 5 of 50 to 200Åon the silicon oxide film 4, and the silicon oxide film 6 of 50 to 200Åon the silicon oxide film 5.
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