Abstract: A low temperature annealed Cu silicide or germanide layer on the surface of a single crystalline semiconductor substrate of Si or Ge is used in interconnection metallization for integrated circuits. The Cu silicide or germanide layer is preferably formed by heating Cu deposited on a Si or Ge substrate up to about 200.degree. C. for about 30 minutes. The layer demonstrates superior (near ideal) current/voltage characteristics and can be used as a high temperature (600-800.degree. C.) stable Ohmic/Schottky contact to Si or as a Cu diffusion barrier. Additional embodiments involve a Cu layer on a Ge layer on Si substrate, a Cu layer on a Si.sub.x Ge.sub.1-x layer on a substrate, and the use of an intermediate layer of a refractory metal such as W.