Ge is deposited on an ultrathin SiO2 layer obtained chemically at room temperature, followed by annealing process. High density and uniform Ge quantum dots, rather than superdomes in traditional treatment, are obtained. Growth mechanism is suggested to explain the unusual microstructure dependence on annealing temperature. Raman spectrum is used to investigate the strain. Two peaks are found to be around 500 nm and 1350 nm respectively from the photoluminescence characterization.