A polyimide (PI) has been used for the passivation of maximum 7.8 kV 4H-SiC P+N–N+ (PiN) diodes with a 60 µm-thick base epilayer and a junction termination extension (JTE) periphery protection. The dielectric strength of PI films is studied versus area and temperature. The reverse electrical characterization of the PI–passivated PiN diodes is presented for different natures of the environmental atmosphere. The results are compared to those obtained from same devices passivated with a deposited SiO2 thick film. The highest experimental breakdown voltages are obtained for PI–passivated PiN diodes immersed in PFPE oil, with a 5-6 kV typical value, and a 7.3 kV maximum value. Experimental observations are discussed in correlation with the insulating film properties.