There is provided a method for selectively etching a first region of silicon oxide with respect to a second region of silicon nitride by performing plasma processing on a target object including the second region formed to have a recess, the first region provided to fill the recess and to cover the second region, and a mask provided on the first region. The method includes: (a) generating a plasma of a processing gas containing a fluorocarbon gas in a processing chamber where the target object is accommodated and forming a deposit containing fluorocarbon on the target object; (b) generating a plasma of a processing gas containing an oxygen-containing gas and an inert gas in the processing chamber; and (c) etching the first region by radicals of fluorocarbon contained in the deposit. A sequence including the step (a), the step (b) and the step (c) is repeatedly performed.