A semiconductor element, a manufacturing method thereof and an operating method thereof are provided. The semiconductor element includes a substrate, a first well, a second well, a third well, a fourth well, a bottom layer, a first heavily doping region, a second heavily doping region, a third heavily doping region and a field plane. The first well, the bottom layer and the second well surround the third well for floating the third well and the substrate. The first, the second and the third heavily doping regions are disposed in the first, the second and the third wells respectively. The field plate is disposed above a junction between the first well and the fourth well.