Photonic SOI devices are formed by lateral epitaxy of a deposited non-crystalline semiconductor layer over a localized buried oxide created by a trench isolation process or by thermal oxidation. Specifically, and after forming a trench into a semiconductor substrate, the trench can be filled with an oxide by a deposition process or a thermal oxidation can be performed to form a localized buried oxide within the semiconductor substrate. In some embodiments, the oxide can be recessed to expose sidewall surfaces of the semiconductor substrate. Next, a non-crystalline semiconductor layer is formed and then a solid state crystallization is preformed which forms a localized semiconductor-on-insulator layer. During the solid state crystallization process portions of the non-crystalline semiconductor layer that are adjacent exposed sidewall surfaces of the substrate are crystallized.