Methods of locally changing the BOX layer of a MOSFET device to a high-k layer to provide different Vts with one backside voltage and the resulting device are provided. Embodiments include providing a Si substrate having a BOX layer formed over the substrate and a SOI layer formed over the BOX layer; implanting a high current of dopants into at least one portion of the BOX layer; performing a high-temperature anneal of the BOX layer; forming first and second fully depleted silicon-on-insulator (FDSOI) transistors on the SOI layer, the first FDSOI transistors formed above either the BOX layer or the at least one portion of the BOX layer and the second FDSOI transistors formed above the at least one portion of the BOX layer; and applying a single voltage across a backside of the Si substrate.