in gas dome system semiconductor international july 1999 the single crystalline cu interconnect may then serve also as a mechanical support for a multilayer gas dome ic structure it will be understood that this invention is not limited to the above illustrated substrate materials conductor materials and materials used to make the diffusion barrier as long as other criterion understood and set forth herein for these respective materials are satisfied in the mode of the invention being discussed above in which metal halides are used as precursor compound for forming the diffusion barrier film the precursor compounds that can be used include for example baf 2 bacl 2 srf 2 srcl 2 csfl and cscl and the like especially preferred are those metal halide salts that have face centered cubic structure e g a cubic fluorite in another mode of the invention for forming the diffusion barrier film the monolayer of metal atoms portion thereof alternatively can be formed in a one step operation i e without a post growth anneal step to decompose excess metal halide by directly depositing an elemental form of the metal atoms such as barium via mbe on the surface of the semiconductor substrate since certain elemental metals such as barium are highly reactive appropriate precautions have to.