The initial growth of titanium germanosilicide on Ge/Si(1 1 1) has been investigated and the role of a Ge buffer layer has been clarified. The surface morphologies and atomic structures were observed using AFM and STM. Ti films with 0.3-3.3 nm thicknesses were deposited at room temperature (RT) or high temperature (HT). In the reaction of a thin Ti (1.7 nm) with Si, only the island-like C49 structures were formed at 650 degreesC annealing. When the Ge buffer layer of 4 ML (0.62 nm) was added, the strip-like C54 structures were also observed. The Ge buffer layer could lower the temperature of phase transformation from C49 to C54 structures. In the case of a ultra-thin Ti (0.55 nm), C54 structures were formed on Ge/Si(l I 1) even at 550 degreesC annealing. When 1.7 nm Ti was deposited on the HT Ge/Si substrate (650 degreesC). nearly all structures formed were of C54. This indicates that the ultra-thin Ti evaporation and HT methods are effective at the initial growth. It was also found that C54 growth reflects the surface of the atomic structures.