The dry etching of II-VI compounds is important for the device processing as it has higher degree of etch selectivity and anisotropy. Different techniques for plasma generation have been discussed. Set up of ECR system with various components and the generation of ECR plasma has been described. The book consists of ECR etching of III-V and II-VI group compound materials. The etching experiments were carried out by changing the various parameters like temperature, etching time, flow rate, microwave power and RF power. UV-Vis spectroscopic study of the etched samples has been made which is discussed in detail. ECR etching of cadmium zinc telluride, one of the II-VI compound materials has been performed by using gas mixture of CCl2F2 and Ar. The CCl2F2 gas is chosen for the etching purposes because of its less toxicity in comparison to pure Cl and other Cl based gases. Structural, thermal and optical properties of II-VI compounds and their various applications have also been discussed. In one chapter the optical properties of the amorphous films have been investigated when the films have been exposed to the ECR discharge.