| 摘要 |
PROBLEM TO BE SOLVED: To provide a high voltage transistor in which variation in drain block ing voltage can be reduced and reduction in channel length can be realized without causing degradation of the transistor performance. SOLUTION: A drain region 20 and the gate electrode 30 in a field-effect transistor is in a state of offset by forming a LOCOS oxidation film 22 at the drain side between the drain region 20 and the gate electrode 30. A channel at a channel region 1a is made by extending the impurity diffusion layer 24 at the drain side to beneath the LOCOS oxidation film 22 at the drain side, and the impurity diffusion layer 24 at the drain side is composed of a first equal concentration region 24a formed at the side of the channel region 1a and a second equal concentration region 24b formed at the side of the drain region 20, and the impurity concentration of the first equal concentration region 24a is configured to be lower than the of the second equal concentration region 24b.
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