The improvement of deposition processes from solutions need a better understanding of the phase formation processes at the atomic level. This study concerns chemical bath deposition of chalcogenide semiconductors (CdS, ZnS, CdSe). Correlations between the growth mechanism and the structure of the films are established from Transmission Electron Microscopy (TEM) and High Resolution TEM measurements. Two dominant mechanisms are evidenced from structural studies, an atom by atom process for CdS and a cluster by cluster process for ZnS and CdSe. Structural defects in CdS are identified. Possible relations with optical properties and composition of the layers are given.