| 摘要 |
PROBLEM TO BE SOLVED: To provide a high voltage transistor whose breakdown voltage on a body substrate is high wherein a low voltage transistor can be sued for a high-voltage application, high gain is expected with accurate matching by the transistor, and only diffusion of an existing well is required. SOLUTION: High breakdown voltage transistors (30 and 30') are formed in a well arrangement. In this arrangement, at least a part of shallow and much doped well (44) is provided in a deep and less doped well (50), with both wells formed in an epitaxial layer (43) of a substrate (42). The deep well (50) is used to form a high voltage transistor, by itself, as well while the shallow well (44) is used to form a low voltage high-performance transistor by itself. With this configuration, a high-performance transistor of accurate matching can be used for a high bias voltage application, with no fear of breakage at the junction of body substrate (in short, 'back gate-substrate').
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