The growth mode of thin films is studied by Auger electron spectroscopy (AES) in comparison with the observations by electron microscope (EM). The simple criteria to discriminate by AES between the nucleation and growth (NG) and the monolayer overgrowth (MO) modes, which take account of the different trends of coverage of substrate surface by overgrown film, are shown to give consistent results with EM: Pd/MoS2, PbTe/MgO are NG and Pd/Au, Au/Pd, Ag/Au, Pd/Ag, GeTe/PbSe are MO. The case of GeTe/PbTe, which gives antinomic features in EM, is decided by AES to be MO. The values of escape depth for several Auger electrons are determined and compared with previous data. The problems of interdiffusion across the interface in MO are discussed.