Contribution of interface traps to valence band electron tunneling in PMOS devices

The I-V characteristic of the negatively biased p-poly PMOS changes from near valence band electron injection to near conduction band electron injection. The Fermi level is the reference energy level for valence band electron tunneling rather than the valence band edge, which results in a voltage dependent barrier height. The proposed Interface State Injection Model explains this by electron injection from interface states, quickly recharged by band to trap tunneling due to the small depletion layer width in highly doped gate material.