This paper discusses reactive ion etching (RIE) process issues in preparing thin-film transistors (TFTs) for liquid crystal displays (LCDs). Three areas were examined in detail: gate metal etch, dielectric etch, and a-Si:H etch, both intrinsic and n+ doped. Although there are different requirements for each step, the basic principles for the etching process are similar. For example, each process includes three major mechanisms: plasma-phase chemistry, particle transport phenomena, and surface reactions. All data on the etching results were interpreted according to these principles. Finally, a TFT characteristic curve based on RIE of some of the most critical process steps is presented.