Diamond film deposition on Si “benchmark” substrates is experimentally investigated at high pressures using a microwave plasma disk reactor and CH4/H2 gas mixtures. In this microwave plasma reactor the plasma is formed inside a 12.7 cm diameter disk-like discharge region located at one end of an internally tuned cylindrical cavity applicator. A water cooling stage is employed to control substrate temperature. The input variables of the experimental evaluation are (1) methane concentration, expressed as c = %CH4H2 from 1∼8%, (2) total flow rate, ft, 200∼1400 sccm, (3) substrate temperature TS which varies from 700∼1125°C, (4) deposition time, t, 5 ∼ 100 h, (5) pressure, p, 80 ∼ 140 Torr, (6) incident power, Pinc, 2 ∼ 4.5 kW. The output films deposited on 2 in. diameter substrates were characterized by (1) growth rate in μm/h and mg/h, (2) film morphology, and (3) Raman spectra. In particular film growth rate versus CH4H2, flow rate, TS and t were performed on films deposited uniformly (<15%) over 2 in. diameter Si substrates. 5 h experiments indicated that the average film growth rate (over 2 in. diameter) varied from a few μm/h with c = 1% to 4.3 μm/h at c = 3% and then decreased for high c ratios. Average growth rate also varied with flow rate with a maximum of over 5 μm/h (∼ 35 mg/h). Growth rate increases as deposition time increases and reaches a maximum growth rate of 6.3 μm/h (∼44 mg/h) at t = 100 h. The film growth reaches a maximum around TS = 1100°C for both 2 and 3% chemistries.