containing gases such as si 2 h 6 si 3 h 6 sih n x 4 u2212 n where x is a halide the present invention offers several advantages in accordance with the invention a thin layer of silicon rich material is formed only at the boundary of the transition metal nitride film thus the silicon rich layer does not affect the overall electrical properties of the diffusion barrier this effect results in superior suppression of copper diffusion without high barrier resistivity further the formation of high resistivity silicon nitride ternary phases is avoided fig4 shows a graph of secondary ion mass spectrometry sims profiles of two 200 u00e5 thick tin si layers deposited on a sio 2 substrate by cvd the horizontal axis is the distance below the surface in angstroms the left vertical axis is the atomic concentration of oxygen and carbon in atoms per ccm the right vertical axis is the intensity in counts per second cps for silicon tin and ti the silicon peaks at the surface and 200 a below the surface represent the silicon rich layers formed by the exposure of the tin surface of each layer to sih 4 the underlying sio 2 begins at 400 u00e5 below the surface fig5 is a graph generated by x ray photoelectron spectroscopy xps showing the chemical state of the silicon incorporated in the tin si the measured silicon data indicates the presence of both si n and si ti bonding and silicon nitride ternaries which are known to have excellent barrier properties fig6 shows the results of bias temperature tests that were performed on an mos capacitor consisting of a sandwich of cu u2014 sio 2 u2014 si each layer being 100 u00e5 thick the test structure is illustrated in the inset the.