AbstractSOI‐like structures produced by N2+ implantation (nitrogen doses, D = 1×1017 cm–2 and 8.5×1017 cm–2, energy 140 keV) into Czochralski grown silicon (Cz‐Si) and subsequent processing of Cz‐Si:N at up to 1520 K (HT) under atmospheric or enhanced hydrostatic pressure (H P, up to 1.4 GPa) were investigated. The main HT–HP induced effects in Si:N are following: formation of buried porous SiNx layer, decreased Si/SiNx interface roughness and improved uniformity of layer thickness, decreased concentration and / or dimensions of defects within the top silicon layer and the substrate, suppressed formation of exfoliation defects in the top silicon layer and decreased size of silicon nanocrystals at the Si/SiNx interface. Subsequent treatment of Si:N resulted in a creation of buried layers with interesting properties, especially in respect of formation of nano‐structured areas. Porosity of buried layer depends on nitrogen concentration and can be tuned by specific treatment conditions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)