In the present work, we apply a 2D self consistent model of SiH4/H2 discharges in order to investigate the transition from microcrystalline to amorphous silicon growth. The model is used to examine the relative importance of ions and atomic hydrogen in the film growth process. This examination also involves monitoring the changes that take place in the electrical properties of the plasma, the gas phase as well as the surface chemistry near the transition between the two growth regimes. Based on these results, the discussion is extended to the mechanism of a-Si:H to μc- Si:H growth transition and the use of plasma diagnostics that can be used to monitor this transition. Keywords: Micro Crystalline Si, deposition, PECVD, thin film