A new ion source with a large beam diameter generated by an electron cyclotron resonance microwave plasma source is presented. Ion beams with a beam diameter of >160 mm and a maximum argon-ion current density of 2.1 mA/cm(2) are obtained. For this large two-electrode silicon-ion extraction optics are mounted into an electron cyclotron resonance microwave plasma source. With ion extraction optics installed an electron temperature up to three times higher than without optics was observed. Due to this high electron temperature (up to 12 eV) the O+ concentration is enhanced in an oxygen plasma. Therefore, a concentration as compared to the O-2(+) an ion current density of 1.1 mA/cm(2) can be generated. Ion energies of 1 keV corresponding to the screen grid voltage are obtained with a small energy spread of 10 eV full width at half maximum or less. The low working pressure (about 10(-4) mbar) is well suited for low-pressure ion-beam processes.