Iron silicides were formed by annealing of iron films evaporated onto silicon wafers and capped with either amorphous silicon or SiO(x) thin overlayers. Pure semiconducting beta-FeSi2 phase was formed at 600-degrees-C during 2 h annealing in nitrogen gas. Beta-FeSi, was formed by reaction with the Si substrate and no reaction with the capping layers was observed at temperatures < 800-degrees-C. After 2 h annealing at 950-degrees-C only the metallic alpha-FeSi2 phase was detected, and the initiation of the reaction of Fe with the amorphous silicon overlayer was observed.