A microwave plasma reactor (MPR) is constructed as a facility for the plasma assisted chemical vapor deposition (PACVD) process. The reactor is a mode-adjustable resonance cavity of cylindrical shape. A 2.45 GHz microwave generator is used to ignite the plasma inside the lengthadjustable cavity. The diamond-like carbon (DLC) thin film depositions onto the silicon substrates are carried out using H2–CH4 discharge. The Schottky barrier diodes (SBD) are then formed on to the DLC films. The responses of DLC-SBD to DC and time varying signals have been studied as a function of frequency. The frequency dependent response results are compared to the computer models, which includes as input parameters the bulk series resistance, the capacitance associated with the bulk material between the space-charge layer and the ohmic contact, the space-charge layer capacitance, and the diode dynamic resistance.