A new multi-phonon model for hydrogen desorption at Si/SiO2 interface due to hot carriers is proposed for a multi-scale simulation, in which Lattice Monte Carlo method is coupled with Device Monte Carlo method by using a mediator-based common software platform. The power law between interface trap density and time (Nit tα) of which power α =0.5 is demonstrated and shows good agreement with experimental results. Dependence of Vth shift on the current stress time is analyzed accurately by introducing an electron trap model. According to the multi-phonon mechanism, it is found that hot carriers will generate defects on the gate dielectrics in 13 nm gate device under low operation voltage of Vd=0.5 V but density of interface traps after long stress time is suppressed to 1015 m-2.