This paper describes the first results of the new Leybold Leybold circular electron cyclotron resonance (CECR) technology which uses circular polarized microwave excitation for generating a plasma of very high density. At a pressure of 1 μbar, an ion current density of 6 mA/cm2was measured in a pure chlorine plasma. That reveals in fact an increase of about 30% in ion density compared to the linear polarized electron cyclotron resonance (ECR) source. The appreciable improvement will be demonstrated by etching results of silicon trench with chlorine where an etch rate of 300 nm/min with a uniformity better than ±5% on 200 mm wafer size was obtained. The source has a compact design which enables multichamber processing in a cluster tool environment with the capability for processing wafers up to 200 mm diameter.