Molecular layer deposition of silicon carbide is described. A deposition precursor includes a precursor molecule which contains silicon, carbon and hydrogen. Exposure of a surface to the precursor molecule results in self-limited growth of a single layer. Though the growth is self-limited, the thickness deposited during each cycle of molecular layer deposition involves multiple “atomic” layers and so each cycle may deposit thicknesses greater than typically found during atomic layer depositions. Precursor effluents are removed from the substrate processing region and then the surface is irradiated before exposing the layer to the deposition precursor again.