This study reveals that the mechanism of leakage current in the oxynitride is deviating from that in conventional grown silicon oxide in the electric field ranging trom 6MV/cm to 14MV/cm and suggests that the electronic conduction is governed by three different mechanisms.The current conduction at electric field lower than 8MV/cm is due to the tunneling of electrons into the shallow traps in the insulator.In high-field region （>10MV/cm）

Fowler-Nordheim（FN）effect becomes dominant but depends on the dielectrics preparation conditions.In moderate field region

traps can be filled by both FN current and direct tunneling of electron into the traps.It results in a quasi-saturation in the leakage current.On the other hand

as the nitrida-tion proceeds

turnaround behaviors are found in leakage current level

ledge in current-voltage characteristics

and fied-dependency of the current.