Isolated diamond crystals have been deposited on silicon by the microwave plasma assisted chemical vapor deposition technique (MPCVD) using the bias enhanced nucleation (BEN) step. The true epitaxial ratio, defined as the number of epitaxied crystals to the total crystal number before coalescence, has been calculated by high-resolution scanning electron microscopy coupled to image analysis software. This ratio is correlated to the conditions of the etching step which precedes the bias step. This investigation allows us to determine the better conditions to obtain homogeneous epitaxied deposit with an optimum epitaxial ratio in the absence of a preceding carburization step, and to propose a qualitative explanation about the effect of the etching step on the silicon substrate.