WS2 thin films (100 nm thick) have been obtained by solid-state reaction, induced by annealing, between W and S constituents sequentially deposited in thin film form. When annealed at 820 K the properties of the thin films appears to be improved with the annealing time (2-145 h). However there is progressive saturation and the grain size remains small (less than or equal to 10 nm), while the texturation of the crystallites, c axis perpendicular to the plane of the substrate, tends toward 100% as shown not only by X-ray diffraction but also by selected area diffraction. The conductivity measurements are in accordance with these results : the conductivity of the sample increases with the annealing time. However it is always controlled by the grain boundaries. Some improvement of the electrical properties of the layers can be obtained by annealing treatment in iodine atmosphere : the conductivity and the homogeneity of the grain boundaries increase, due to the iodine passivation of traps at the grain boundaries.