The formation of PtSi and Pd2Si on chemically cleaned and on slightly oxidized Si substrates had been investigated by TEM with cross-sectional specimens. The oxide has been found to influence the silicide-Si interface roughness, the silicide surface roughness,and the corrosion behavior of the silicide layer. The formation of PtSi is more sensitive to the presence of oxide than Pd2Si and may even be suppressed. Remnants of the oxide are identified within the silicide using Auger sputter profiling technique. They can be interpreted as diffusing markers and provide information about the diffusing atomic species. Results of such marker experiments for formation of Pd2Si and PtSi are disussed.