The formation of ytterbium silicide fabricated by annealing at 480 °C for one hour has been studied by means of high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). The annealing process has been performed under ultra high vacuum (UHV) conditions. The formation of an amorphous silicide layer was observed between the Yb-layer and the silicon substrate in the as-deposited sample. Ytterbium silicide observed after annealing consists of two different layers: crystalline and amorphous ones. The studies confirmed that the formed crystalline layer is of the YbSi phase, however, the structure is different from the hexagonal AlB type.