| 摘要 |
In a semiconductor device including high-voltage, middle-voltage, and low voltage transistors having operating voltages different from one another, a gate length and a thickness of a gate oxide film are increased as the operating voltage is increased. Accordingly, in the high-voltage transistor, an electric field produced at a channel is relaxed. In the low-voltage transistor, a structure is made finer. A concentration of a well and an impurity amount implanted into a surface portion of a substrate are set to be identical with each other in all the transistors. Accordingly, the semiconductor device can be speedily manufactured at a high yield.
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