We discuss a new method for plasma enhanced chemical vapor deposition, called low energy plasma enhanced chemical vapor deposition (LEPECVD), applied to the epitaxial growth of Si and SiGe heterostructures. Growth rates up to 5 nm/s become possible at substrate temperatures below 600 degrees C, by utilizing very intense but low energy plasmas to decompose the reactive gases, SiH4 and GeH4, and by supplying non-thermal energy to enhance the surface kinetics. We have applied LEPECVD to the synthesis of step-graded SiGe buffer layers, and studied them by scanning force microscopy and X-ray reciprocal space mapping.