Embodiments herein describe techniques for a semiconductor device over a semiconductor substrate. A first bonding layer is above the semiconductor substrate. One or more nanowires are formed above the first bonding layer to be a channel layer. A gate electrode is around a nanowire, where the gate electrode is in contact with the first bonding layer and separated from the nanowire by a gate dielectric layer. A source electrode or a drain electrode is in contact with the nanowire, above a bonding area of a second bonding layer, and separated from the gate electrode by a spacer, where the second bonding layer is above and in direct contact with the first bonding layer.