SOI (silicon on insulator)-structures were produced by implantation of 330 keV, 14N+-ions with doses ranging from 0.9 to 1.5 × 1018 cm−2 at a target temperature of 500°C into monocrystalline silicon to form buried silicon nitride layers. Post-implantation annealing was done at 1200°C up to 5 h. In this manner silicon nitride compounds with different stoichiometry and structure are produced. After implantation amorphous layers with Gaussian nitrogen profiles up to overstoichiometric concentrations are formed. Annealing leads to the transformation of the Gaussian profiles into rectangular ones if the maximum concentration of the as-implanted distribution does not exceed the value necessary for Si3N4 stoichiometry. In all cases the interfaces between the buried layer and the neighbouring silicon are steep and the structure of the silicon nitride is crystalline. For stoichiometric and overstoichiometric layers a high resistivity in the range of 1014 to 1016 Ω cm was found. After annealing monocrystalline silicon top layers of high quality are formed. A test is reported on the reamorphization of crystalline Si3N4. The results are promising.