SEMICONDUCTOR DEVICE MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method which forms more improved pattern shapes of a resist layer, an intermediate layer, and a resist layer.SOLUTION: A semiconductor device manufacturing method comprises: forming a lower layer photoresist 7, an intermediate layer 8 of an inorganic material, and an upper layer photoresist 9; patterning the upper layer photoresist 9 to form an upper layer resist pattern 9a; installing a semiconductor substrate 1 in a chamber on a lower electrode; introducing a first reaction gas having a sulfur dioxide gas and an oxygen gas into the chamber to generate plasma and cutting off supply of a high-frequency power to the lower electrode to trim the upper layer resist pattern 9a; replacing the first reaction gas with a second reaction gas and supplying a high-frequency power to the lower electrode to etch the intermediate layer 8 by using the upper layer resist pattern 9a as a mask to form an intermediate layer pattern 8a; and replacing the second reaction gas with a third reaction gas to generate plasma and supplying a high-frequency power to the lower electrode to etch the lower layer photoresist layer 7 by using the intermediate layer pattern 8a as a mask.