A highly reliable SiO2/Si3N4/SiO2 (ONO) dielectric with an equivalent SiO2 thickness of about 40 nm and a poly-Si gate is demonstrated on n-type 4H-SiC. Dielectric breakdown strength of BEOox = 21 MV/cm and 18 MV/cm is achieved at room temperature and 300° C, respectively. It is shown that the maximum allowable current density, BJO(ox), is in the 10 A/cm(2) range and two to three orders of magnitude higher than that of a single thermal oxide and that the leakage cur-rent density is dramatically reduced in the E-ox, range above 7.5 MV/cm. A TDDB test conducted on about 50 capacitors at room temperature under constant current stress revealed charge-to-breakdown of Q(BD) = 30 C/cm(2) at the 50 % failure point.