The growth of FeSi2 on Si(111) by gas source molecular-beam epitaxy is reported. Fe(CO)5 and SiH4 are used as source gases for the silicide growth on the heated substrate. A wide range of growth temperatures, 400–800 °C, has been examined and the thickness of the grown layers ranges between 50 and 200 nm. High resolution electron energy loss spectroscopy, with its sensitivity to the electronic properties of heterostructures in a range of several hundreds angstroms below the surface, turns out to be very effective for the in situ characterization of the growth. Photoelectron spectroscopy and ex situ high-resolution transmission electron microscopy complete this study. Three main growth modes are identified. For Tgrowth≤500 °C, different phases are growing, with an early stage of β-FeSi2 nucleation. Above 550 °C only the semiconducting β phase is formed with increasing tendency towards three dimensional growth as the temperature increases. In the range 500–550 °C the β-FeSi2 layer grows uniformly and the presence of a p++ accumulation layer, ∼100 Å thick, at the surface is inferred. This accumulation layer is removed by room-temperature adsorption of dissociated SiH4.