The growth mechanism of TiO2 films and their morphology are reported using the reactive-layer-assisted deposition (RLAD) method under ultrahigh vacuum conditions. The oxide film formation involves Ti atom deposition on top of amorphous solid water (ASW) condensed on a SiO2/Si(100) support at 90 K. Subsequent annealing leads to the desorption of all nonreacted buffer molecules, resulting in the deposition of the titanium oxide film. Employing mass spectrometry and using D2O as a buffer, we detected the evolution of deuterium molecules during titanium atom deposition. A solid state sol-gel-like formation mechanism of titanium oxide is proposed on the basis these observations. The morphology of the oxide films is characterized by AFM as a rather uniform amorphous thin film at room temperature. Upon further annealing above 750 K, crystallization of the titanium oxide film has set in, coinciding with a dewetting process of the oxide layer, and information obtained from similar growth procedure on an amorphous carbon-covered TEM grid. It was shown that these films are rather insensitive to the underlying substrate at temperatures below 500 K.