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The conduction mechanism of ultra-thin gate oxide n-metal-oxide-semiconductor fi eld effect transistor (n-MOSFET) after soft breakdown is studied in this paper. It is found that in a certain range of gate voltage Vg, the gate cur r ent Ig follows the Fowler-Nordheim-like tunneling mechanism, and the experimen tal tunneling barrier b is 0936 eV in average, which is much smal ler t han the interface barrier of Si/SiO2 We think that after soft brea kdown, the electrons existing in the quantization energy levels of the Si/SiO2 interface , not directly tunnel to the oxide conduction band, but tunnel to the oxide defe ct band. b is determined by both the defect band energy level and t he qu antization energy level of the tunneling electrons. With rising experimental tem perature, the tunneling of high energy level electron is also increasing, which reduces b gradually.

Interference method is introduced to study the Fowler-Nordheim tunneling current oscillations. An accurate and simple formula for measuring the oxide thickness and the electron effective mass in the conduction band of the oxide is given.A comparison between the results calculated directly from the Schrdinger equation and those from the interference method for the triangular barrier case shows that the interference method suits very well for studying Fowler-Nordheim tunneling current oscillations.The interference method reveals the wave nature of the electron tunneling in the barrier.An important feature of this method is that it may be applicable to various shapes of potential barriers and wells. We also analyze the experimental results and give the physical meanings of them.