MULTISTAGE CVD METHOD FOR THIN-FILM TRANSISTOR

PROBLEM TO BE SOLVED: To provide a method of depositing a SiNx layer and an a-Si layer on a thin film transistor(TFT) substrate at a sufficient deposition rate keeping high film quality. SOLUTION: A material layer near the interface of an a-Si layer is deposited at a low deposition rate, so as to be extremely high in quality, and a material layer distant from the interface is deposited at a high deposition rate to be somewhat lower in quality than the former material layer but sufficiently high in quality. Through this method, a g-SiNx film 54 which is of high quality and deposited at a low deposition rate is deposited on the top surface of a g-SiNx film 52, which is of average quality and deposited at a high deposition rate, and then an a-Si layer is deposited thereon, whereby a TFT of extremely high quality can be efficiently manufactured. At this point, an a-Si layer of high quality is deposited on a g-SiNx layer at a low deposition rate to form an interface 56, and an a-Si layer of average quality is deposited thereon at a high deposition rate to have the formation of an a-Si layer 58 completed. This method can be applied to an interface between an a-Si layer and an active semiconductor layer, and the method can be also applied to a back channel type or an etching stop type TFT.