This paper describes the characteristics of thin fluoride films on InP which are used as dielectric for metal‐insulator‐semiconductor (MIS) devices. Films of Ba1−xSrxF2(x=0.0, 0.5, 0.83, and 1.0) were deposited by sublimation of mixtures of BaF2and SrF2in vacuum under 10−5Torr pressure. The composition of the films was deduced from x‐ray diffraction and energy dispersion analysis by x‐ray studies. The electrical activation energies of the films determined between 120 and 300 K were found to be 3.5–22.0×10−3eV , depending on composition and temperature. The resistivity of the films was in the range of 5.0×1011to 5.0×1012&OHgr; cm with the breakdown fields greater than 5.0×105V cm−1. The interface state density obtained was as low as 5×1010cm−2 eV−1with annealed BaF2films. Scanning electron microscope studies showed that annealing caused development of cracks resulting in decreased film resistivity. Auger studies gave evidence of broadening of the interface and outdiffusion from the substrate due to annealing.