A field device and method of operating high voltage semiconductor device applied with the same are provided. The field device includes a first well having a second conductive type and second well having a first conductive type both formed in the substrate (having the first conductive type) and extending down from a surface of the substrate, the second well adjacent to one side of the first well and the substrate is at the other side of the first well; a first doping region having the first conductive type and formed in the second well, the first doping region spaced apart from the first well; a conductive line electrically connected to the first doping region and across the first well region; and a conductive body insulatively positioned between the conductive line and the first well, and the conductive body correspondingly across the first well region.