We have studied the three-stage deposition process of CuGaSe2 (CGS) films, with the help of spectroscopic light scattering (SLS) in situ monitoring method. During the second stage (i.e. deposition of Cu, Se), an abrupt change from a two-layered structure to a single layer, together with a significant increase in the grain size, was observed in the vicinity of the Cu/Ga = 1.0 point. Shortly before this abrupt change, a characteristic peak was observed by SLS, accompanied by a definitive change in depth-oriented distribution of Cu and Na. (c) 2004 Published by Elsevier B.V.