Basic properties of transition metal oxide films as a high‐resolution, negative working ion resist have been studied experimentally for focused ion beam (FIB) exposure. Thin amorphous films of WO3, MoO3, V2O5and a mixture thereof were formed on Si wafers and exposed to a 20–70 keV Ga+FIB. Development after writing was performed by chemical etching. The resist sensitivity and the contrast were measured as a function of the accelerating voltage of the FIB. The dry etching durability of the delineated resist patterns and their selectivity with respect to Si were also evaluated for SF6plasma etching. The details of the characteristics can be explained in terms of the physical and chemical properties of the resist material.