We report on the microfabrication and testing of a chip- scale plasma light source. The device consists of a stack of three anodically bonded Pyrex wafers, which hermetically enclose a gas-filled cavity containing interdigitated Aluminum electrodes. When the electrodes are powered through an impedance matching circuit, these devices have been used to generate stable millimeter- size RF plasma discharges operating continuously for over 24 hours in He or Ar at pressures ranging from 10 to 500 mbar at RF powers of 300 to 1500 mW.