Dynamically supplied atomic hydrogen was used for a surfactant growth of Ce on a Si(100) surface. The transition from three-dimensional to two-dimensional growth of Ge was observed as the hydrogen flux was increased to similar to 1 ML/s in scanning tunneling microscope images. Layer-by-layer growth was successfully achieved up to 5 ML of Ge in the presence of atomic hydrogen. Observed missing dimer rows, irregular trench structures, and new "pin holes" are believed to be the product of strain relieving mechanism. The layer-by-layer growth can be understood both by energetics and kinetic pathway arguments.