[en] We have fabricated Si nanocrystals utilizing nanometer-sized Pt islands acting as etching-masks on SiO_x/amorphous-Si/SiO_x/p-Si (1 0 0) thin films. In the measurement of transmission electron microscopy the Si nanocrystals embedded in SiO₂ were observed, and in the measurement of cathodoluminescence spectroscopy at 77 K Si nanocrystal-related peaks were observed at 462 and 647 nm. For the Al/SiO₂/nanocrystalline-Si/SiO₂/p-Si capacitor structure, a hysteretic behavior with the flatband voltage shift of 0.592 V was observed in the measurement of capacitance-voltage characteristic at 300 K. These results indicate that Si nanocrystals can be formed by using a nanosized Pt island etching-mask, and that Si nanocrystals embedded in SiO₂ layer act as Si quantum dots which hold promise potential applications