This paper describes short-gas-residence-time electron cyclotron resonance plasma etching for high etch rates, reduced contamination, and highly anisotropic etching. The new high-gas-flow-rate (high-flow) etching system is demonstrated with effective-pumping rate of 2500 l/s. This method produces very high etch rate while maintaining high anisotropy at very low gas pressure below 1 mTorr. The high etch rate is due to the reduction of reaction products density because of the very short gas-residence time of 30 ms. This technique also dramatically reduces the contamination of reaction products. Etching of crystalline Si and n+ polycrystalline Si with the high-flow etching system is demonstrated. For crystalline Si etching with Cl2, a high etch rate up to 1/mum/min is achieved at a high gas flow rate of 90 sccm at 0.5 mTorr.