A general review of mathematical treatments on this redistribution phenomena has been made and discussed. A series method is developed and exact solutions describing the redistributed impurity concentration profiles in both the oxide and the semiconductor can be given. Boundary conditions of diffusion equations are discussed according to different physical situations. Special cases are treated for three initial impurity concentration profiles in silicon: Gaussian, complementary error function, and uniform. Experiments were performed on boron‐doped silicon by wet oxygen at 1200°C. The initial concentration profile was a Gaussian, and the segregation coefficient was found to be about 1.8.