Abstract: A dry etching method according to one embodiment of the present disclosure includes plasmatizing a dry etching agent and etching a silicon oxide or a silicon nitride with the plasmatized dry etching agent, wherein the dry etching agent comprises CF3I and a C2-C3 fluorine-containing linear nitrile compound, and wherein the concentration of the C2-C3 fluorine-containing linear nitrile compound relative to the CF3I is higher than or equal to 1 vol. ppm and lower than or equal to 1 vol %.