Discrete midgap tungsten nanocrystals (W-NCs) embedded in atomic layer deposited hafnium aluminate (HfAlO) film were fabricated by a self-assembly method using sputtering followed by rapid thermal annealing and integrated into transistors for nonvolatile memory application. Transmission electron microscopy and single electron diffraction analysis revealed the formation of crystalline W-NCs (similar to 5 nm) embedded in an amorphous HfAlO matrix. Effects of deposition of thin Al2O3 on the formation of W-NCs were investigated. Al2O3 was found to be effective to retain the amorphous property of the underlying HfAlO, assisting to form uniformly distributed and small W-NCs. Electrical characterization of the Si/HfAlO/W-NCs/HfAlO structure based memory device showed that clear memory effects (1.8 V memory window at operating bias of 7 V) and good retention properties (50 mV/dec threshold voltage decay rate) originate from the charge storage of electrons in W-NDs and deep quantum well of W-NDs embedded in the HfAlO+Al2O3 high-k structure. (c) 2005 American Vacuum Society.