SrS:Ce films were investigated by secondary ion mass spectrometry (SIMS) in order to examine the luminescent center distribution in the phosphor before and after annealing. Cerium was accumulated near the interfaces between the phosphor and insulating layers, and this accumulation was most extensive in the phosphor annealed in H2S. The Ce accumulation is found to shift the electroluminescent (EL) emission spectra to a longer wavelength. It is also found that crystallinity improvement of the SrS phosphor by annealing in H2S causes Ce accumulation and the presence of oxygen enhances the Ce accumulation.