The improved data retention characteristics of Polysilicon-oxide-hafnium oxide-oxide-silicon (SOHOS) type nonvolatile memory were obtained by post-HfO2 trapping layer deposition tetrafluoromethane (CF4) plasma treatment. The memory characteristics such as program/erase speed, retention and endurance were studied comprehensively. That fluorine atoms incorporated into Hf-based high-k material eliminate shallow trap defect level effectively and remain deeper trap level. Although the shallow traps of the HfOF trapping layer SOHOS memory have passivated, it doesn't deteriorate the program/erase speed obviously and retention characteristic was then improved because of deeper electron storage level. The results clearly indicate CF4 plasma treatment-induced deep electron storage level is a feasible technology for future SOHOS-type nonvolatile flash memory application.