Previously an asymmetric double well potential model was successfully applied to interpret the nonlinear relaxational polarization of al 2 o 3 . here we extend this model to hfo 2 . the capacitance measurements on hfo 2 based metal-insulator-metal mim capacitors were performed. to study this relaxational polarization the thickness of the dielectric, device temperature, frequency and electric field were varied systematically. it was revealed that at lower temperatures t ⩽ 180 k the relaxation happens via proton tunneling transition in asymmetric double wells. incorporation of protons