A semiconductor apparatus is disclosed. The semiconductor apparatus includes an SOI substrate including an active layer, a buried insulation film and a support substrate; a low potential reference circuit part located in the active layer and operable at a first reference potential; a high potential reference circuit part located in the active layer and operable at a second reference potential; a level-shifting element forming part located in the active layer and for providing a level-shift between the first and second reference potentials; and an insulation member insulating first and second portions of the support substrate from each other, wherein locations of the first and second portions respectively correspond to the low and high potential reference circuit parts.