Electronic properties of Cu/Ta/SiO2/Si structures are strongly affected by the temperature dependence of atomic diffusion behaviors. increasing the annealing temperature from 800 to 950 degreesC, the sheet-resistance was anomalously reduced from 0.88 to 0.16 Omega/cm(2). It is believed that Ta layer was oxidized to form Ta2O5 at 950 degreesC in which the diffusion channels could not be formed. Therefore, the individual Cu. atoms could only cross the Ta2O5 layer percolating into SiO2 through the stacking faults. This diffusion behavior significantly restricted Cu migration at such a high temperature, thus reducing the sheet-resistance to a value close to the value observed in as-deposited sample. (C) 2004 Elsevier B.V. All rights reserved.