A manufacturing method of a semiconductor device includes etching a film using etching gas that has a first or second molecule which has a C3F4 group and in which the number of carbon atoms is four or five. Further, the first molecule has an R1 group that bonds to a carbon atom in the C3F4 group through a double bond, and the R1 group contains carbon and also chlorine, bromine, iodine, or oxygen. Further, the second molecule has an R2 group that bonds to a carbon atom in the C3F4 group through a single bond and an R3 group that bonds to the carbon atom in the C3F4 group through a single bond, the R2 group or the R3 group or both containing carbon, and both the R2 group and the R3 group containing hydrogen, fluorine, chlorine, bromine, iodine, or oxygen.