A parallel plate/narrow gap radio frequency (RF) (400 kHz)-plasma SiO2 etching reactor for a 200 mm diam wafer was scaled up to that for a 300 mm diam wafer according to numerical simulations of gas flow and mass transfer for the etching gas CF4/Ar. Experimental measurements of this reactor (for a 300 mm diam wafer) agree well with the simulated etching rate anti etching, uniformity on the 300 mm diam wafer. It was shown that the reactor for a 300 mm diam wafer could be scaled up only in the radial direction. It was also clarified that gas inlet showerhead radius and plasma radius correlatively affect the etching rate at the edge of the wafer; they are therefore key parameters that must be controlled to get better uniformity of etching rate.