| 摘要 |
PURPOSE:To form a structure, in which threshold voltage is set easily while maintaining high withstand voltage characteristics, by making carrier concentration in a surface area to be a channel lower than one in the other area in a conductivity type diffusion region for forming the channel. CONSTITUTION:A second conductivity type diffusion region 2 for shaping channels is formed to the surface of a first conductivity type semiconductor region 1', and gate electrodes 5 are shaped onto surface areas 2b as the channels through insulating layers 12''. Carrier concentration in the surface areas 2b as the channels in the second conductivity type diffusion region 2 is made lower than that in other areas of said region. That is, even when carrier concentration in the surface areas 2b as the channels is lowered in order to be set within a practical threshold voltage range, a punch-through is difficult to be generated between a source and a drain because carrier concentration in other areas is made higher than that in the surface areas 2b. Accordingly, threshold voltage can easily be set while maintaining high withstand voltage characteristics.
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