A charge retention characteristic of a nonvolatile memory transistor is improved. A first insulating film that functions as a tunnel insulating film, a charge storage layer, and a second insulating film are sandwiched between a semiconductor substrate and a conductive film. The charge storage layer is...http://www.google.se/patents/US7851296?utm_source=gb-gplus-sharePatent US7851296 - Nonvolatile semiconductor memory device
