We investigated the boron (B) incorporation ratio ((B/C)(film)) in chemical vapor deposition (CVD) homoepitaxial diamond films as a parameter of the misorientation-angle (theta(off)) of substrates under the partial step-flow condition of (CH4/H-2)(gas)=0.3%. The boron concentration in a diamond network, N-B, strongly depends on theta(off). This suggests that there are two processes for incorporation of boron atoms in a diamond network: one is caused by step-flow growth and the other is caused by island growth on a terrace of a growing diamond surface. Using a simplified model focusing on the step-flow growth in which a boron atom embedded in the top layer is desorbed from the surface with a certain probability, we analyzed the mechanism by which boron is incorporated into diamond CVD films. (C) 2011 Elsevier B.V. All rights reserved.