The results of analytical and numerical solutions of the problem of the redistribution of elements between the coating and the substrate under heat treatment are presented here. It is assumed that the coating consists of two elements - chromium and nitrogen, and the substrate is silicon. The model takes into account the Soret effect. The Soret’s coefficients (or the corresponding coefficients of thermal diffusion) are different for the elements. The analytical solution of the linearized coupled problem is obtained by the operational method. Numerical solution was implemented by implicit difference scheme. In the linear approximation, the results of numerical solutions are close enough to analytical ones. The effect of diffusion coefficients and thermal diffusion on the redistribution of elements in the diffusion zone has been studied.