Diamond film was deposited in CO and H2 gas mixture by microwave plasma assisted chemical vapor deposition (MPCVD). Bias enhanced nucleation and two-step growth method were employed. Scanning electron microscopy (SEM), Raman spectroscopy and transmission electron microscopy (TEM) were used to characterize the film. It was found that twins and stacking faults were mainly produced at the stages of nucleation and growth. In the second growth stage, the production of defects in the film was reduced considerably, resulting in the final smooth-faceted diamond grains with five-fold symmetry or parallel twins with a small amount of stacking faults. At the edge of the sample, there was a region with low nucleation density, which might be the result of non-uniform plasma existing there. Meanwhile, a non-diamond structure of carbon was found in the edge region.