Two-dimensional (2D) materials represents nowadays the new frontiers of semiconductor technology [1]. At one side, great effort has been done in research applied to graphene producing new technology that will rebuild many industrial sectors. On the other side non-graphene 2D materials like transition metal dichalcogenides (TMDs) are highly attractive because they offer complementary properties to graphene [2] but still lack a large-scale production method for high quality and well controlled layers. MoS2, one of the most studied TMDs materials, has been produced by using many techniques, but the deposition through chemical methods, ie based on the use of materials such as Mo or MoO3 and then the reaction with sulfur, already demonstrates to fit better the stringent requirements of lateral uniformity on the centimeter scale, vertical scalability and structural optimization as function of the growth parameters [3]. However, many details about the chemistry of the reaction between Mo precursor and sulfur needs further clarification in view of a large-area production [4]: in particular, it is not clear the role of the materials used as precursors, of the substrate type and of the deposition temperature, which drives Mo-S reaction, but also other undesired ones. This work is focused on the study of some of these fundamental parameters in the growth of MoS2 on SiO2/Si substrates by vapor-solid chemical reaction between Mo pre-deposited thin film precursor (TFP) and sulfur (figure 1 (a)). We demonstrate that the control of the Mo film thickness allows us to have accurate control of the MoS2 thickness. This methodology leads to MoS2 nanosheets with a …