Method for manufacturing transistor, transistor, and display device

A method for manufacturing a transistor according to the present invention includes: a first step for forming, on an insulating substrate (10), a metal film used for a gate electrode (11); a second step for forming a gate insulating film (12) which covers the metal film; a third step for forming, on the gate insulating film (12), a non-crystalline silicon film having a film thickness in the range of 25 to 55 nm; a fourth step for irradiating the non-crystalline silicon film with light that has a wavelength in the range of 380 to 495 nm, and changing the non-crystalline silicon film to a crystalline silicon film (14); a fifth step for forming a non-crystalline silicon film on the crystalline silicon film (14), and forming a channel layer comprising the crystalline silicon film (14) and non-crystalline silicon; and a sixth step for forming, above the channel layer, a metal film used for a source/drain electrode (17).