A method is provided for forming a semiconductor device. The method includes providing a substrate on a substrate holder in a process chamber, where the substrate contains a raised feature having a top surface and a sidewall surface, and flowing a process gas into the process chamber, where the process gas contains a hydrocarbon gas, an oxygen-containing gas, and optionally argon or helium. The method further includes maintaining a process gas pressure of at least 1 Torr in the process chamber, forming a plasma from the process gas using a microwave plasma source, and exposing the substrate to the plasma to deposit a conformal amorphous carbon film over the surfaces of the raised feature.