Prospects of polyethersulfone (PES) foils as a thermally and chemically stable substrate for the deposition and thermal processing of semiconductor thin films are presented. The particular example here is CuS thin films of 75–100 nm thickness deposited from a chemical bath constituted using copper(II) chloride, sodium citrate and thioacetamide on PES transparent foils of 25-μm thickness. The electrical conductivity of the coatings varies in the range of 10 3 Ω −1 cm −1 to 10 4 Ω −1 cm −1, the sheet resistance is in the range 10 Ω/□ to 100 Ω/□. The sheet resistance remains in this range even after the films are annealed at temperatures up to 300°C, the minimum value of sheet resistance (10 Ω/□) and the maximum electrical conductivity (10 4 Ω −1 cm −1) are attained when the films are annealed at 200°C. The near infrared transmittance of the coated foils is approximately 75% at a wavelength of 2.5 μm, which is related to the electrical conductivity of the CuS coating. The sheet resistance of a PES foil coated with CuS film of 100 nm thickness and subsequently annealed at 200°C in nitrogen remains constant at ∼10 Ω/□ even after it was maintained in dilute HCl solutions of 0.1 M and 1 M for up to 150 min. Fourier transform infrared spectra recorded in the attenuated total reflection mode show that the PES substrates are stable up to temperatures of 300°C. X-Ray diffraction studies have confirmed that the copper sulfide thin films maintain a composition CuS at such temperatures.