An approach to grow high quality strain-relaxed Ge on silicon (1 0 0) substrate has been proposed using a modified two-step growth method by reduced pressure chemical vapor deposition system. The modified Ge growth method consists of the low temperature growth at 400 degrees C, intermediate temperature growth from 400 to 600 degrees C with low ramping rate and high temperature growth at 600 degrees C. The post-growth anneal in hydrogen at 800 degrees C was introduced immediately after the Ge growth. For the Ge epitaxial film grown with low temperature ramping rate of 6 degrees C/min, the root mean square roughness is 0.621 nm in 10 X 10 mu m(2) scan field, and the threading dislocation density (TDD) is 3 X 10(6)cm(-2) with the film thickness of about 1.3 mu m. Furthermore, in contrast to the epitaxial Ge sample grown with the high temperature ramping rate of 140 degrees C/min, intermediate low temperature ramping rate from 400 to 600 degrees C is advantageous in terms of TDD reduction, as well as maintaining smooth surface morphology in Ge epilayer. (C) 2014 Elsevier B.V. All rights reserved.