A method for forming buried ion-exchanged waveguides involves a two-step process. In a first step a waveguide is formed at the surface of a substrate using an ion-exchange technique. After formation of the waveguide, a field-assisted annealing is carried out to move the waveguide away from the surface of the substrate so that it is buried in the substrate. Exemplary field-assisted annealing is carried out at a temperature close to the ion-exchange temperature ±10° C. to optimize results.