There were obtained nanodimensional AlN layers on Si by HVPE (Hydride Vapor Phase Epitaxy) method. SEM (Scanning Electron Microscopy) images of AlN layers, and cross-sections of AlN/Si structures are shown. The structure of surface layers was investigated by AFM (Atomic Force Microscopy) method at the stage of forming continuous layer. AlN grains nucleation on the surface of silicon occurs according to the three- dimensional (Folmer -Weber) mechanism. Granules represent a statistically dispersed ensemble of particles distributed on the substrate surface. Two mechanisms have been identified for estimating grains in the transition from the germination stage to the stage of continuous layer formation.