Resolved! MOS FET with built-in TVS diode.
I want help to understand this. The STM MOS FET STP6NK60ZFP has a MAX gate-source voltage (Vgs) at 30V. In order to protect it from ESD it has a built-in TVS diode. Over 30V it can fail. But the bulit-in TVS has breakdown voltage (Vbr) set at 30V. It...