SEMICONDUCTOR DEVICE MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To provide a technology capable of improving reliability of a semiconductor device; and especially a technology capable of obtaining stable performance characteristics in a semiconductor device having a field effect transistor with a gate electrode composed of a metal material.SOLUTION: A semiconductor device manufacturing method comprises: forming a gate electrode 13n or a gate electrode 13p by dry etching using a resist pattern 12 as a mask; subsequently, performing an ashing treatment in a plasma atmosphere containing oxygen and hydrogen to remove the resist pattern 12; oxidizing a reaction product 14 adhered to a lateral face of the gate electrode 13n or the gate electrode 13p; and subsequently, performing a cleaning treatment to remove the reaction product 14.