We propose a multistep procedure for Ge dot growth on Si (1 0 0) substrates. This procedure includes (i) submonolayer C deposition on a Ge wetting layer or a Ge surface, (ii) Ge deposition at low temperature and (iii) postannealing after Ge and C deposition for controlling size, structure and density of the Ge dots. The main effect of C on Ge wetting layer was to enhance a structure transition of the Ge dot. Meanwhile, C on the Ge surface was found to suppress a structure modification of the Ge dots against post-annealing. The structure of Ge layers deposited at low temperature was readily modified upon post-annealing. By combining these procedures and optimizing experimental conditions, 10 nm-sized Ge dots with a high number density in the order of 10(11) cm(-2) were successfully grown on the Si (1 0 0) substrate.