Abstract: A method of fabricating a thin-film transistor, includes the step of forming a source region and a drain region in a semiconductor thin film having a capping film thereon, by accelerating a plasma source including hydrogen ions and one of Group III ions and Group V ions of the Periodic table, and simultaneously implanting the hydrogen ions and one of the Group III ions and the Group V ions into the semiconductor thin film, wherein there exist a plurality of peaks in a depth profile of a concentration of the hydrogen ions implanted into the semiconductor thin film having the capping film thereon and a second peak from a surface of the capping film among the plurality of the peaks is made to exist in the semiconductor thin film.