Thin films of boron carbon nitride (BCN) and boron carbide (BC) were synthesized by plasma enhanced chemical vapor deposition (PECVD) using two different reactant chemistries: (i) N,N’,N” – trimethylborazine (TMB); (ii) dilute diborane (5% in Ar) and hydrocarbon as precursor materials. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Nano-Indentor, Flexus stress instrument and x-ray photoelectron spectroscopy were used to study the deposited films. The BC films are much more stable than BCN films under high humidity (100%) environment. Both BCN and BC films are very stable under atmospheric conditions. A high compressive stress of -4.2 GPA was achieved by conventional PECVD, which show promising applications in high performance ultra large-scale integrated circuit (ULSI) devices.