Silicon Carbide (SiC) devices are a technology used for power electronics and especially for automotive applications. For MOSFET devices, an aging of the Gate oxide with dynamical HTGB stress called GSS on a commercial device permits a better understanding of the failure mechanism occurring on the device during use. Electrical static characterization Ids-Vds and Ids-Vgs, Raman spectroscopy, Atomic Force Microscope associated with a "resiscope" and Transmission Electronic Microscopy analyses are used to determine the composition of the oxide design and the origin of the failure mechanism. An electrical modification related to a nanometer scale material variation with platelet apparition is detected through the oxidation.