Low temperature poly-Si TFT technology is reviewed and is discussed from a view point of device, fabrication process, and its possibility as FPD (Flat Panel Display) application. After the appearance of crystallization technique of SPC (Solid Phase Crystallization) using FA (Furnace Annealing) or ELA (Excimer Laser Annealing) using UV (Ultra-Violet) beam, the electronic property of poly-Si thin-film, which relates to the crystalinity of the grains, was improved drastically, and the process temperature for the TFT fabrication had been reduced below 600° down to 400°. As a result, improvement of device characteristic of poly-Si TFT such as an enhancement of carrier mobility or a reduction of leakage current has been studied intensively for the application to FPD (Flat Panel Display) on glass. Currently, extensive study is being done in order to realize a more functional SOG (System on Glass). By reducing the TFT process temperature down to 200° or below and by modifying a design for the device structure or the circuit in the pixel, O-LED (Organic LED) FPD addressed by uniform poly-Si TFTs is expected to mount on flexible plastic substrate such as on PES (PolyEtherSulphone). The poly-Si TFT has a possibility to develop as a smart system on plastic panel for unique applications as well as the conventional Si LSI in the ubiquitous IT (Information Technology) era.