Shumpei Yamazaki, Koichi Hatakeyama, Ichiro Kagawa and Yoshinari Yamashita

Nonvolatile memories are now focused by many people.　One of the most popular structure of the memories is an MNOS（metal-silicon nitride-silicon oxide-semiconductor） structure.　However the structure has poor memory retention when B-T （80℃, -10V） stress is applied to the sample. The developed structures are MNCOS and MNCNOS （metal-over silicon nitride-silicon clusters-under silicon nitride-semiconductor）, in which the silicon clusters are the small polycrystalline silicon particles having a compressed hemisphere. As the clusters act as trap centers of both holes and electrons, the trapping efficiency of centers increases, and the thicker silicon oxide film (tox = 50 - 60 A) is able to use for the better memory retention.　The memories can operate more than ten years under the BT （-10V, 80℃） stress condition.

『1973年　IEDMより抜粋』