| 摘要 |
In a conventional semiconductor device, for example, a MOS transistor, there is a problem that a parasitic transistor is prone to be operated due to an impurity concentration in a back gate region and a shape of diffusion thereof. In a semiconductor device of the present invention, for example, a MOS transistor, a P type diffusion layer 5 as the back gate region, and an N type diffusion layer 8 as a drain region, are formed in an N type epitaxial layer 4 . In the P type diffusion layer 5 , an N type diffusion layer 7 as a source region and a P type diffusion layer 6 are formed. The P type diffusion layer 6 is formed by performing ion implantation twice so as to correspond to a shape of a contact hole 15 . Moreover, impurity concentrations in surface and deep portions of the P type diffusion layer 6 are controlled. By use of this structure, a device size is reduced, and an operation of a parasitic NPN transistor is suppressed.
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