The electron storage characteristics of Ge/Si hetero-nanocrystal metal-oxide-semiconductor field-effect transistor memory are investigated by computer simulation. Owing to the Ge/Si hetero-energy bands, the retention time increases several orders compared with that of Si nanocrystal memory, and the programming time achieves the order of us. The trade-off between the high-speed programming and the long retention time could be solved efficiently with the present Ge/Si hetero-nanocrystal structure.