High-quality poly-Si microstructure is needed for the fabrication of high-quality poly-Si TFTs. The crystallization process is a very critical step of the thin film transistor (TFT) fabrication process, as it needs to satisfy conflicting requirements on material quality and cost and, at the same time, comply with the thermal-budget constraints imposed by the display substrate. Historically, solid-phase-crystallization (SPC) was the first technology to produce poly-Si films for display applications, followed by the development of laser-annealing crystallization (LAC). Both of the technologies evolved significantly over the past 20 years with a variety of spin-offs that aimed at improving different features of the poly-Si crystallization process and/or the poly-Si microstructure. This paper discusses the motivation behind the evolution process in the crystallization technology. We discuss in detail the different aspects of various crystallization techniques and provide the rationale behind our belief that lateral-crystallization technology possesses the best collection of features to enable the formation of very high-quality poly-Si films compatible with the fabrication of state-of-the-art, ultra-high performance poly-Si TFT devices. (C) 2002 Elsevier Science B.V. All rights reserved.