| 摘要 |
A non-volatile semiconductor memory device (50) includes, formed in successive layers on a substrate (10), a silicon oxide layer (13), a silicon oxynitride layer (14), a silicon nitride layer (15), a further silicon oxynitride layer (16) and a silicon gate electrode (19). At least one of the oxynitride layers (14, 16) is of graded oxygen:nitrogen composition. An alternative embodiment includes only a single oxynitride layer (14) formed on the oxide layer (13), the single oxynitride layer (14) being graded. The grading of the oxynitride layers (14, 16) is in incremental steps. The oxynitride layers (14, 16) and the nitride layer (15) are formed by low pressure chemical vapor deposition at the same temperature. The devices have the advantage of high retention. |
