C-B-N films have been deposited by chemical vapor deposition from methylamine (CH3-NH2) and diborane (B2H6) gas mixtures. For methylamine-rich mixtures (r = [CH3-NH2][B2H6] = 6), the deposition reaction is thermally activated, showing a low apparent activation energy (E-a = 7.1 kcal/mol). In gas mixtures with lower methylamine flow rates (r = 1), the reaction is also thermally activated in the 350-550 degrees C range, the apparent activation energy being slightly higher (16 kcal/mol). In the last case, for temperatures higher than 550 degrees C the deposition rate decreases at increasing temperatures. At these temperatures, the methylamine is decomposed to methane, ammonia, hydrogen, and hydrogen cyanide, thus changing the deposition reaction. In this temperature range (>550 degrees C), increasing content of methylamine in the gas mixture produces initially an increase in the deposition rate to a maximum followed by the subsequent decrease for the higher methylamine content. The composition of the deposited films has been analyzed by infrared spectroscopy (IR) and surface analytical techniques (Auger electron spectroscopy and X-ray photoelectron spectroscopy). Graphite carbon is always present in the deposited films. Metallic boron, also present in the films, decreases in the 350-800 degrees C range, favoring the formation of the ternary CBN compound. At temperatures higher than 800 degrees C, the deposited films consist mainly of a mixture of the CNB ternary material (note a new sequence of atoms in the ternary compound), in addition to boron nitride and graphite carbon. The results of the variation of the deposition rate have been explained by two simultaneous processes: (i) the chemical reactions for the C-B-N film formation, which are enhanced by the increase in the reactant concentrations as well in the deposition temperature and (ii) the parallel adsorption on the substrate surface of methane molecules, coming from the methylamine decomposition, which can disturb the deposition process.