Abstract Silicon nitride is employed for insulating layers, surface passivation layers and antireflection coatings. In this paper, we report on the influence of the addition of H 2 gas to N 2 gas and the total gas pressure on the nitride layer formation on a hydrogenated microcrystalline silicon (μc-Si:H) film surface region. Following deposition of the μc-Si:H thin films, a post-deposition treatment was carried out using a hot-wire chemical vapor technique, in a mixture of N 2 /H 2 or in a N 2 atmosphere, at varying H 2 gas flow rates and total gas pressures, to form a nitride layer in the film surface region. As the H 2 gas flow rate, F (H 2 ), was increased from 2 to 10 sccm, at a N 2 gas flow rate, F (N 2 ), of 20 sccm, the surface nitridation was dramatically enhanced. Conversely, the degree of surface nitridation remained virtually unchanged with a F (H 2 ) of 10 - 15 sccm and the surface nitridation scarcely took place at F (H 2 ) of 20 sccm. The surface nitridation occurred to some extent at 0.1 Torr (with F (N 2 ) = 20 and F (H 2 ) = 10 sccm) but was dramatically enhanced as the gas pressure was increased from 0.1 to 1.0 Torr. There was a reduction in the densities of both the N and Si atoms as the gas pressure was increased from 1.0 to 6.0 Torr, however, the density of the N atoms on the subsurface region of the films (at a depth of 20 nm from the surface) increased with increasing gas pressure. These findings show the breakdown of the Si network structure by high density H radicals and the diffusion of more N atoms into the deeper region of the films.