US Patent 7361567 - Nanocrystal nonvolatile memory with graded nitrogen content

http://www.freepatentsonline.com/7361567.html

The use of nanocrystals in some non-volatile memory designs has helped decrease gate leakage. However, electron trapping can be caused due to the nanocrystal layer. This patent from Freescale Semiconductor teaches using a graded nitrogen content to avoid this problem. Claim 1 reads:

1. A method for forming a semiconductor device comprising: providing a semiconductor substrate; forming a first insulating layer over a surface of the semiconductor substrate; forming a layer of nanocrystals over a surface of the first insulating layer; and forming a second insulating layer having a graded nitrogen content over the layer of nanocrystals.