An effect of the time constant of the measurement setup on a breakdown behavior of SiC MOS capacitors with aluminum gate electrode was investigated. For this experiment, an additional series resistance was inserted into the TDDB and TZDB measurement system. With respect to TDDB, SBD occurred more frequently when the additional series resistance was inserted. It is speculated that the joule heat generated at the moment of breakdown was not sufficient to form a low resistance conduction path between the gate electrode and substrate. With respect to TZDB, a sequential formation of separated groups of concaves was observed when the additional series resistance was inserted. It is speculated that the post-breakdown resistance was high enough to cause 'self-healing' as observed in the TDDB measurement. These results highlight the generation and dissipation of the heat at the time of the breakdown is one of the causes that determine HBD or SBD of SiC MOS capacitors.