To solve the dilemma between long retention and scaled tunnel oxide, in this work, engineered floating gate, such as hybrid-nanocrystal and new materials nanocrystals that are compatible with current Si technology, was proposed and good memory performance was demonstrated. Chapter 1 introduces the conventional flash memory, including the operation principle, architectures, challenge in next generation flash memory and some new technologies to address this issue in conventional flash. Chapter 2 describes the methodologies used in this thesis work, including nanocrystal growth methods, nanocrystal characterization techniques, and nanocrystal memory fabrication and device characterization. Chapter 3 discusses the flash memory with Ge/Si hetero-nanocrystals as floating gate. Type-II band alignment between Ge and Si makes Ge/Si hetero-nanocrystal good for long time hole storage than Si nanocrystal memory. In addition to p-MOS, we also developed n-MOS memory with CoSi 2 -coated Si nanocrystals as floating gate in the Chapter 4. The Fermi-level of CoSi 2 locates around the midgap of Si so that the device is good for both electrons and holes trapping. Furthermore, the quantum well formed between CoSi 2 and SiO 2 is deeper than that of Si and SiO 2, leading to an elongated retention time. The Si nanocrystal underneath the CoSi 2 effectively prevents the charges stored in CoSi 2 from leaking back to the channel. In order to lower the thermal budget to make silicide nanocrystals, vapor-solid-solid (VSS) growth mode was employed and NiSi 2 nanocrystsals were synthesized as presented in Chapter 5. The long retention of NiSi 2 nanocrystal memory is also benefited from the deep quantum well between NiSi 2 and SiO 2. For next generation flash memory, more uniform nanocrystals with higher dot density, 10 12 cm -2, is necessary to meet the requirement of 22nm technology and beyond. In Chapter 6, we developed PtSi nanocrystals using the similar synthesis technique as NiSi2. The nanoc