Two-bit SONOS type Flash using a band engineering in the nitride layer

A novel film in the trapping layer of SONOS device has been proposed. With gradually changing Si/N content ratio, the nitrogen-rich in middle (NRM) nitride has better performance and reliability than a conventional standard Si3N4film. This new configuration can increase trapping efficiency by adding the probability of lateral hopping and reduce charge loss tunneling back to substrate from nitride. Besides, the characteristics of the two-bit operation are exhibited in this study. The SONOS of NRM nitride is suitable for a localized trapping storage promising non-volatile memory application.