Embodiments disclosed herein include transistor devices and methods of forming such transistor devices. In an embodiment a transistor comprises a substrate, and a fin that extends up from the substrate. In an embodiment, the fin comprises a source region, a drain region, and a channel region between the source region and the drain region. In an embodiment, the transistor further comprises and a cavity in the fin, where the cavity is below the channel region. In an embodiment, the transistor further comprises a gate stack over the fin.