The silicon nitride (a-SixNy:H) contact etch stop layer strongly affects data retention performances. in single polysilicon nonvolatile memories by acting on the initial charge loss phenomenon. Its improvement has required an analysis of influent plasma enhanced chemical vapor deposition process parameters through a design of experiment approach. The a-SixNy:H physico-electrical analysis points out that silicon rich compositions especially of its interfacial layer must be avoided to reduce a-SixNy:H charge amount and as a result to improve the data retention. Indeed, the a-SixNy:H being near the floating gate, its charges modulation could act as a parasitic memory screening charges stored in the floating gate by capacitive effects. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3071846]