Threshold-alterable Si-gate MOS devices

An electrically threshold-alterable n-channel MOS device with polysilicon gate is experimentally realized by employing a polysilicon-oxynitride-nitride-oxide-silicon (SONOS) structure. Because of several high-temperature processing steps after the nitride deposition, it was found necessary to increase the thin-oxide thickness of the SONOS devices in order to achieve better charge retentivity. It has been shown that the SONOS device can be used in MOS integrated circuits. Some memory and switching characteristics of the SONOS devices with oxide thickness of ∼30 Å are presented.