Gettering efficiencies of copper, whose bulk concentrations are lower than 1 ϫ 10 12 atoms/cm 3 in p-type silicon, have been evaluated quantitatively and the results are reported. Bulk copper introduced by intentional spiking and subsequent heat-treatment was shown to be gettered by bulk microdefects ͑BMDs͒, which had been introduced by heat-treatment prior to intentional contamination using a 65 Cu isotope tracer as a probe. For evaluation of gettering efficiencies, we found the trace analysis of the 65 Cu isotope to be critical and, thus, developed a procedure for trace analysis of bulk copper in the silicon bulk by modifying the published analytical technique, which allowed gettering efficiencies to be quantitatively evaluated for copper levels of below 10 12 atoms/cm 3 . We also describe a few other parameters important to the evaluation of gettering efficiencies, including outdiffusion of copper through the silicon matrix, formation of BMDs, and low-temperature out-diffusion.