Embodiments described herein generally relate to methods and apparatus for horizontal gate all around (hGAA) isolation. A superlattice structure comprising different materials arranged in an alternatingly stacked formation may be formed on a substrate. The different materials may be silicon containing materials and one or more III/V materials. In one embodiment, at least one of the layers of the superlattice structure may be oxidized to form a buried oxide layer adjacent the substrate.