Novel CVD precursors for SiBxCyNz film deposition such as HCCB[N(SiMe3)2]2, MeB[N(SiMe3)2]2 and Me3SiCCB[N(SiMe3)2]2 were synthesized. The structure and composition of the compounds were investigated with NMR, FTIR, Raman spectroscopies and CHN-analysis. Comparison of theoretical and experimental FTIR and Raman data was performed. Thermogravimetric analysis and the static tensimetry method with a glass membrane null manometer demonstrated that Me3SiCCB[N(SiMe3)2]2 is the most suitable CVD precursor. The formation of SiBxCyNz films was predicted using thermodynamic modelling at a temperature below 1600 K in the total pressure range of 0.27-1333 Pa. The films of chemical composition Si23.7B8.3C51.4N9.6O7 were deposited by low-pressure chemical vapour deposition (LPCVD) and their morphology and mechanical properties were investigated. The amorphous SiBxCyNz films with a smooth surface exhibited hardness, Young's modulus and elastic recovery equal to 17.5 ± 0.9 GPa, 176 ± 11 GPa and 61 ± 2%, respectively.