A new plasma enhanced chemical vapour deposition (CVD) technique, referred to as closed chamber CVD (CC-CVD), is presented. It is based on a process, which alternates the deposition of an ultra-thin layer and modification at equilibrium conditions within a temporarily closed reactor chamber. Results on the preparation of highly crystalline muc-Si:H films at an increased growth rate are presented. An emphasis is given to the specific opportunities of CC-CVD to control the structural details of the muc-Si:H material. Efficient p-type doping of ultra-thin muc-Si:H layers was also demonstrated. Phase-pure a-SiC:H films - with carbon dominantly bonded in a Si-C configuration - are also prepared by CC-CVD. They simultaneously have a large band gap and a high conductivity. Because of the enhanced capability of CC-CVD to control the structure of the deposited films, it is an appropriate technique for the synthesis of various Si-based thin film materials for application in large area electronics.