| 摘要 |
In a semiconductor substrate having a first well of a conductivity type opposite to that of the semiconductor substrate, formed on part of a main surface of the semiconductor substrate, a second well of the same conductivity type as the semiconductor substrate, formed on part of a surface region of the first well shallower than the first well, and a third well of a conductivity type opposite to that of the semiconductor substrate, formed in a surface region of the first well, in a region where the second well is not formed and shallower than the first well, by having a fourth well, formed in a region of the main surface of the semiconductor substrate where the first well is not formed and doped with impurities of the same conductivity type as the semiconductor substrate at a lower concentration than the third well, and controlling a reference voltage to be low, it is possible suppress the occurrence of a latch up phenomenon. |
