Patent ID: 7009246

Claim:
A semiconductor device comprising: a semiconductor substrate of a first conductivity type; first, second, and third wells being each of a second conductivity type opposite to said first conductivity type and provided in said semiconductor substrate; a first field-effect transistor being of a first channel conductivity type and driven by a first supply voltage, and a second field-effect transistor driven by a second supply voltage larger in absolute value than said first supply voltage, the first and second transistors being arranged in said first well; a third field-effect transistor being of said first channel conductivity type and driven by said first supply voltage, the third transistor being arranged in said second well; a fourth field-effect transistor being of a first channel conductivity type and driven by said second supply voltage, the fourth transistor being arranged in said third well; a first isolation layer provided between said first and second field-effect transistors; and a second isolation layer provided between said first and second wells and between said second and third wells, wherein said second supply voltage is supplied to said first well, said first supply voltage is supplied to said second well, said second supply voltage is supplied to said third well, and said second isolation layer is wider than said first isolation layer.