The capacitance-voltage characteristics of metal-insulator-semiconductor structures based on Hg1-xCdxTe (x = 0.218) with CdTe passivation are studied before and after the passivation annealing process. We found that after vacuum annealing at 300 degrees C for 24 h, the micromorphology of the passivation layer was significantly improved, and as the fixed charge density decreased from 1.3 x 10(12) cm(-2) to 1.0 x 10(10) cm(-2), the fast surface state density decreased from 2 x 10(13) cm(-2) eV(-1) to 3 x 10(12) cm(-2 )eV(-1), with a minimum value of 1.2 x 10(11) cm(-2) eV(-1). From these findings, combined with the secondary ion mass spectroscopy analysis, we conclude that the annealing process propagates an equivalent electrical surface for CdTe/HgCdTe uniformly from the principal physical interface to the inside of the bulk material, effectively improving the characteristics of the CdTe passivation layer. (C) 2020 Author(s).