Characterization of a-SiC:H films deposited by hexamethyldisilane (HMDS) in remote hydrogen plasma is carried out and a reaction model for film deposition is presented. The Si/C ratio increases from 0.6 to 1.3 while the optical bandgap decreases from 3.3 to 2.1 eV with an increase in substrate temperature from 30 to 600-degrees-C. When the chemical aspect of the deposition process is concerned it was found that atomic H decomposes the HMDS molecule via a chemical reaction. UV radiation appears to be inactive during the deposition process. It is proposed that the most susceptible bond for the initial breakup is the Si-Si bond in the HMDS molecule. We assume that the other possible bond for the initial break up is C-H. A reaction model for the deposition of a-SiC:H is presented by considering Me2Si = CH2 as the film-forming precursor.