TiO2 Atomic Layer Deposition (ALD) is used in microelectronics due to its ability to produce conformal thin films whose thickness is controlled at the subnanometer scale. Tetrakis(dimethylamido)titanium(IV) (TDMAT) and water are frequently used precursors for TiO2 ALD, although there are still some differences in growth behavior in the literature. In this parametrical study, the growth of TiO2 was controlled in situ by Spectroscopic Ellipsometry (SE) in combination with ex situ thickness measurements by X-Ray Reflectometry (XRR). The injection and purge times were optimized to reach self-saturation on the surface. We put in evidence two regions of the Growth Per Cycle (GPC) as a function of substrate temperature: GPC decreases from 0.8˚A.cy−1 to 0.5˚A.cy−1 as the temperature rises from 50 ◦C to 200 ◦C, and then GPC increases from 0.6˚A.cy−1 to 0.9˚A.cy−1 as the temperature rises from 250 ◦C to 350 ◦C. There is no evidence of an ALD window. The stoichiometry of the layer grown at 200 ◦C, determined by X-ray Photoelectron Spectroscopy (XPS), is TiO2 (1 Ti atom per 2 O atoms). The 200 ◦C as-grown sample becomes crystalline (Anatase crystals) after annealing 3 hours in air at 400 ◦C, or at 600 ◦C. The initial growth stages of TiO2 were studied by SE and Atomic Force Microscopy (AFM). Regarding TiO2 ALD on (100)Si substrate (with a native SiO2), we observed a substrate enhanced growth which turned into steady-state ALD beyond 20-30 cycles. Additionally, TiO2 ALD on (001)In0.53Ga0.47As substrate demonstrates substrate inhibited growth of type 2 (islands formation) which turned into TiO2 steady-state ALD beyond 20-30 cycles. The results of TiO2 ALD are compared with those of the existing literature.