PtSi films have been formed using different annealing sequences and ambients. Using sputtered Pt, the passivating oxide layer formed on the PtSi films shows a clear dependence on the annealing sequence and ambient used. Using a one-temperature sequence at 550 °C in forming gas (N2-H2 9:1), nitrogen or oxygen, the passivating oxide layers all show very poor resistance against etching in aqua regia, an undesirable condition for device fabrication. This is attributed to the incomplete reaction between Pt and Si using such a process. Using a three-temperature sequence at 200-300-550 °C in forming gas, a much improved oxide is obtained with excellent resistance against etching in aqua regia. The process is shown to allow a complete reaction between Pt and Si, a necessary step for the subsequent formation of high quality surface oxide. The three-temperature process using nitrogen or oxygen, however, shows incomplete reaction between Pt and Si, and surface oxide of poor quality, similar to those obtained by the single-temperature process in various gases. © 1986, American Vacuum Society. All rights reserved.