Nitrogen implantation into single-crystal silicon can result in a buried nitride layer under proper processing conditions. SOI structures have been formed using this technique. The optimum parameters for forming a buried nitride layer with good insulating characteristics have been investigated. Nitrogen was implanted into <100> silicon at 200 keV at an implantatipp tem erature of 500°C. The effect of implantation doses of 1.05 × 1018N+/cm2, 1.3 × 1018N+/cm+ and 1.4 × 1018N+ /cm+ and post-implantation annealing temperatures of 1050, 1100, 1150, and 1200°C on the buried nitride layer was studied. Transmission Infrared Spectroscopy was used to determine the structure (amorphous or crystalline) of the buried nitride layer. The infrared spectra change as a function of annealing temperature, indicating the transition from amorphous to crystalline silicon nitride. Leakage currents through the structures were measured and SEM micrographs of the nitride surfaces were taken. The correlation between the IR results and these data will be presented.