The conventional floating gate NVSM will suffer some limitations for continued scaling of the device structure. The floating gate is a continuous semiconductor thin film which charges are stored in and able to move around. With the scaling of tunneling oxide, the thickness is decreased gradually. Once the tunneling oxide has been created a leaky path, all the stored charges in the FG will be lost after numerous counts of write/erase operation. When the tunnel oxide is thinner, the phenomenon happens more easily but the speed of write/erase operation is quicker. Therefore, there is a tradeoff between speed and reliability.Therefore, two approaches, the silicon-oxide-nitride-oxide-silicon (SONOS) and the nanocrystal nonvolatile memory devices, have been investigated to overcome the limit of the conventional floating gate NVSM. In this thesis, the nonvolatile nanocrystal memory structures were proposed for electrical analysis and physical mechanism studied. We proposed two nanocrystal memory, silicon nanocrystal memory and nickel-silicide nanocrystal memory. The silicon nanocrystal memories have standard sample and nitridation sample. The interface between the nitride and Si-dots can offer extra trap cites for electrons storage. And the nickel-silicide dots memory has standard sample and high-k sample. The HfO2 layer for control oxide can increase the electric field of the tunnel oxide to get better programming efficiency.