Dependence of charge storage and programming characteristics on dot number of floating dot memory

We fabricated a nonvolatile memory with a narrow channel and self-aligned Si nanoscale floating dots and studied the dependence of charge storage and programming characteristics on the dot number along the channel. Almost the same threshold voltage shift in the memory window was observed for devices with one or two floating dots. This indicates that the threshold voltage shift is determined only by the charge in one floating dot even when two floating dots are positioned in series along the narrow channel. Better retention characteristics were obtained for devices with two floating dots than those for devices with one floating dot, while almost the same programming characteristics were obtained. Therefore, the metal-oxide-semiconductor field-effect transistor with multiple self-aligned Si floating dots positioned along the narrow channel in series is a promising candidate for future extremely low power memory having a long retention time without sacrificing programming characteristics.