Ionic contamination of the oxide has been studied in Al/SiO2/3C-SiC capacitors by thermally stimulated ionic current and secondary ion mass spectroscopy analyses. Both sodium and potassium are present in the oxide. The properties of the trapping-detrapping of mobile ions in the oxide have also been studied, and two traps have been characterized. The first one is located at both the SiO2/SiC and Al/SiO2 interfaces and has an activation energy of about 1 eV. The second one is located only at the SiO2/SiC interface and is deeper (1.4 eV). The dependence of these activation energies with the electric field varies as a function of the interface and is slightly different from Al/SiO2/Si structures.