For the first time, a complete 2D transient multiphysics electro-thermo-mechanical and metallurgical model of a 1.2kV-80mOhm gate-planar SiC MOSFET power chip has been developed in a single FEM software. This model is used to quantify the short-circuit critical time and energy density with respect to the local SiO2 interlayer strength at high temperatures and the Al source-metal solidus-liquidus phase transition temperature. Repetitive experimental short-circuits were conducted to confirm the gate-aging existence in coherence with the critical values extracted from the proposed model.