Cu/Ta/PtSi structures are heated between 200 and 700 °C, with Ta as a barrier for improving the thermal stability of Cu/PtSi. A small amount of Cu silicides is observed after a 30‐min anneal in N2‐H2at 300−400 °C. This is accompanied by an extensive mixing among the components present, and increasing sheet resistances. By comparing with the reactions of the Cu/Ta/Si, Al/Ta/PtSi, and Al/Ta/Si structures, the mechanisms suggested earlier are supported, with the high affinity of Cu toward Si playing a major role for the low thermal stability of the Cu/PtSi structures with and without various barrier layers.