In the present study, thermal properties of the electroless-deposited Cu thin film were investigated. The Cu thin film of good adhesion was successfully deposited on the TaN barrier layer by a electroless deposition method. The multilayered structure of Cu/TaN/Si was prepared by electroless-depositing the Cu thin layer on the TaN diffusion barrier which was deposited by MOCVD on the Si substrate. In order to investigate the effect of post-heat treatment the specimen was annealed in H-2 reduction atmosphere. Crystallization and agglomeration of the electroless-deposited Cu film occurred through annealing at H-2 atmosphere and resulted in the decrease of film resistance. Thermal stability of Cu/TaN/Si system was maintained up to the annealing temperature of 600degreesC in H-2 atmosphere above which the intermediate compound of Cu-Si was formed through diffusion into the TaN layer.