| 摘要 |
A conventional semiconductor device has a problem that it is difficult to obtain a desired breakdown voltage characteristic due to a reduction in a punch-through breakdown voltage between drain and source regions. In a semiconductor device according to the present invention, a P type diffusion layer is formed in an N type epitaxial layer. An N type diffusion layer as a back gate region is formed in the P type diffusion layer. The N type diffusion layer is formed by self-alignment using a drain electrode. This structure makes it possible to increase an impurity concentration of the N type diffusion layer in a vicinity of a P type diffusion layer as a source region. As a result, it is possible to improve a punch-through breakdown voltage between the drain and the source regions, and to achieve a desired breakdown voltage characteristic of the MOS transistor.
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