A masking layer is applied over a top semiconductor layer and patterned to expose in an opening a shallow trench isolation structure and a portion of a top semiconductor region within which a first source/drain region and a body is to be formed. Ions are implanted into a portion of a buried insulator layer within the area of the opening to form damaged buried insulator region. The shallow trench isolation structure is removed and the damaged buried insulator region is etched selective to undamaged buried insulator portions to form a cavity. A dielectric layer is formed on the sidewalls and the exposed bottom surface of the top semiconductor region and a back gate filling the cavity is formed. A contact is formed to provide an electrical bias to the back gate so that the electrical potential of the body and the first source/drain region is electrically modulated.