Method for manufacturing thin film transistor having hydrogen feeding layer formed between a metal gate and a gate insulating film

A method for manufacturing a thin film transistor having a source region and a drain region formed in a polycrystalline silicon thin film and a gate electrode formed on said polycrystalline silicon thin film with a gate insulating film interposed between said polycrystalline silicon thin film and said gate electrode, said method comprising:

• a process of forming an island-structured polycrystalline silicon thin film on an insulating substrate;
• a process of forming, after having formed said gate insulating film on said polycrystalline silicon thin film, a micro-crystalline silicon thin film and a metal thin film sequentially on said gate insulating film;
• a process of etching, after having formed a corrosion-resistant mask layer on said metal thin film, said metal thin film using said corrosion-resistant mask layer to form said gate electrode having a desired shape;
• a process of etching said micro-crystalline silicon thin film using said corrosion-resistant mask layer to form a hydrogen feeding layer having an approximately same shape as said gate electrode;
• a process of forming a first insulating film on entire surfaces being exposed containing a surface of said gate electrode;
• a process of selectively implanting an impurity of a conductive type on said polycrystalline silicon thin film to form said source region and said drain region;
• a process of forming contact holes in said first insulating film and said gate insulating film in a manner to expose said source region and said drain region and forming a source electrode to be connected to said source region through one of said contact holes and a drain electrode to be connected to said drain region through another of said contact holes;
• and
• a process of forming a second insulating film on entire surfaces being exposed containing surfaces of said source electrode and said drain electrode,
• wherein each process after having formed said micro-crystalline silicon thin film is performed at room temperature being lower than about 400° C. to prevent hydrogen from being unnecessarily released from said micro-crystalline silicon thin film,
• wherein said process of forming said second insulating film is performed using SiH4, NH3, and H2 as reactant gas at 300° C. to 400° C. simultaneously to feed hydrogen from said hydrogen feeding layer into an interface between said polycrystalline silicon thin film and said gate insulating film, and
• wherein said process of forming said second insulating film is performed in an atmosphere containing hydrogen plasma to improve an efficiency of hydrogenation of said interface.