Fowler–Nordheim (FN) tunneling electron injection was performed in Al/Si oxynitride/Si capacitors and compared with the results for the thermal Si oxides grown at 850 and 900 °C as well as the plasma oxide. The Si oxynitride was grown by direct oxynitridation of the Si substrate using helicon-wave excited nitrogen–argon mixed plasma around room temperature. The shift of the threshold voltageVth[the inversion voltage of capacitance–voltage(C–V)curves] was much larger for the negative stress than for the positive stress, similar to the case ofSiO2.TheVthshifts were much smaller for the plasma-grown Si oxynitride than for the thermal and plasmaSiO2when the oxynitride sample was annealed at moderate temperatures (300–500 °C) in nitrogen ambient. These findings can be explained on the basis of surface plasmon and avalanche breakdown models proposed as the explanation of hot-carrier injection instability inSiO2.When the Si oxynitride samples were annealed at high temperature (800 °C), anomalousC–curves were observed and the degradation was very great, especially for positive bias FN stress. These results are also tentatively explained. ©1997 American Institute of Physics.