A first well in a first conductivity type which is formed at a first region and is electrically connected to a first power supply line, a second well in a second conductivity type being an opposite conductivity type of the first conductivity type which is formed at a second region and is electrically connected to a second power supply line, a third well in the second conductivity type which is integrally formed with the second well at a third region adjacent to the second region, a fourth well in the first conductivity type integrally formed with the first well at a fourth region adjacent to the first region, a fifth well in the first conductivity type which is formed at the third region to be shallower than the third well, and a sixth well in the second conductivity type which is formed at the fourth region to be shallower than the fourth well, are included.