A thin‐film combination containing (2000Å)/poly‐Si (1000Å) has been considered for application as first‐level metallization in large scale silicon integrated circuit devices. The present investigation was made to ascertain the thermal stability of this structure as reflected by changes in microstructure, resistivity, and stresses of these films upon heat‐treatment up to 1000°C. The films (2000Å thick) were formed by sintering Pt on poly‐Si at 700°C (15 min) in vacuo or forming gas; the wafers were then coated with 5000Å of Silox and heat‐treated at various temperatures. No agglomeration was observed at up to 900°C, although a moderate amount of grain growth did take place. The sheet resistance of these films decreased from ∼4 ohm/□ to ∼2 ohm/□ after the 750°C anneal, it then increased with increasing annealing temperature to ∼16 ohm/□ (900°C anneal). The resistivity increase is tentatively attributed to the accumulation of Si at the grain boundaries of . At 1000°C, a liquid‐eutectic phase was formed. However, the liquid did not “ball‐up,” i.e., it wetted and poly‐Si, and on cooling, it precipitated relatively large areas of variously oriented single crystals of Si. This recrystallization process led to a sharp decrease in the sheet resistance of .