Structural, electrical and photoluminescence properties of single crystalline silicon implanted with hydrogen and helium, Si:H and Si:He (ion doses ≤ 5. 1016 cm-2, energy, E ≤ 200 keV) and subjected to annealing at up to 1470K under hydrostatic pressure up to 1.2 GPa were investigated. The temperature - pressure (HT - HP) treatment of Si:H and Si:He results in creation of nanostructured buried layers containing gas - filled cavities and numerous extended and point defects; the HT - HP treated Si:H structures are not splitted contrary to those annealed under atmospheric pressure. The HT - HP induced effects are related to creation of smaller, nanometer - sized structural defects and to retarded out - diffusion of hydrogen and helium at HP. The buried layers are active in respect of oxygen gettering. The Si:H and Si:He samples indicate visible photoluminescence after subjecting to specific HT - HP treatment.