In a method of an embodiment, radicals, which are generated from a processing gas, is adsorbed to a layer to be etched without applying a high-frequency bias to a lower electrode, in an adsorption step. In the subsequent etching step, ions, which are generated from the processing gas, are drawn into the layer to be etched by applying a high-frequency bias to the lower electrode. The adsorption step and the etching step are alternately repeated. In the adsorption step, a density of radicals is 200 or greater times a density of ions. In the etching step, RF energy having a power density of 0.07 W/cm2 or less is supplied to the lower electrode or a high-frequency bias having a power density of 0.14 W/cm2 or less is supplied to the lower electrode for a period of 0.5 seconds or less.