Annealing thin films of silicon containing HfO2 films deposited by an electron-beam coevaporation produces silicon nanocrystals embedded in high-κ dielectric HfO2. Such films can be used to fabricate nonvolatile memory devices. By changing the Si content in the precursor HfSixO2 (x=1, 2, 3, or 4) film, the size and density of silicon nanocrystal could be controlled and high-density of silicon nanocrystals could be obtained. Transmission electron microscopy observations showed that the maximum density of silicon nanocrystals was as high as 1.3×1013 cm-2 for HfSi4O2 and the average nanocrystal diameter was 4.3 nm. The metal-oxide semiconductor capacitor memory structure with embedded silicon nanocrystals in HfSi4O2 exhibited the largest memory window, 3.94 V under ±5 V sweep voltage.