A parallel-plate capacitively coupled microplasma excited by a conventional operating frequency of 13.56 MHz has been generated both in a quartz tube with an inner radius of I or 2 mm and in a capillary, whose cross section is 65-500 mumX500-5000 mum, on a 20 mmX20 mm quartz chip. To attain a plasma ignition at a low rf power without reflection, a pi-type matching circuit was miniaturized and suitably designed to satisfy the resonance condition with the excitation frequency, so that an atmospheric He discharge was obtained at an incident power of 1-3 W. The atomic excitation temperature in the atmospheric discharge was evaluated to be about 1900 K in terms of the atomic emission spectrum. Low-power (2-3 W) glow discharge of pure Ar was also attained at the pressure p given by (pd)(min)=0.5-0.8Torr cm, where d is a discharge gap. The microplasma was applied to the inner-wall modification of a poly(ethylene terephthalate) (PET) capillary to demonstrate the electro-osmosis flow (EOF) control on a microcapillary electrophoresis (CE) chip. We found that the mobility of the EOF (mu(EOF)) of the PET capillary treated by the downstream O-2 plasma was 5.1 X 10(-4) cm(2)/Vs, which is about three times larger than that of the untreated PET capillary.