Diamond films are attractive for both electronic and mechanical applications because of their superior hardness, strength, chemical stability, etc. For applications in MEMS, very smooth thin films are desired. Our main objective was to deposit a smooth and thin diamond film. Diamond films were deposited on 3-inch diameter, p-type, [100] oriented silicon substrates using a microwave plasma disk reactor (MPDR). Four-nanometer diamond powder was used for seeding the silicon wafers. In this paper, we study the effects of the early introduction of methane. The deposition conditions were changed to introduce methane right at the beginning instead of introducing it after about 5 min as was done previously. Due to this change, there was a considerable increase in nucleation density and growth rate. Very smooth films were obtained in the shorter duration depositions. The initial phase deposition revealed some graphite content in the films, which decreased with increasing deposition time.