Multiple-valued memory operation in SiN-based single-electron memory

Multiple-valued memory operation is one of the keys for future high-density memory devices since it significantly increases memory capacity per unit area. We previously reported a single electron memory device that utilizes traps in a silicon nitride (SiN) layer as the memory node and an ultra-sensitive Al/AlO/sub x/ single-electron transistor (SET) for readout (Sunarmura et al., 1999). In this work, we propose a new device structure in which a new layered structure is designed so that only electrons can participate in the device characteristics. With this new device structure, we successfully achieve multiple-valued single-electron memory operation of up to nine values for the first time. An oscillating behavior in SET output current (I/sub SET/) during write/read processes due to electron trapping/detrapping at the traps is used to represent multiple values.