ETCHING METHOD

An etching method is provided. A processing target object includes a first region made of silicon oxide and a second region made of silicon nitride. The second region is extended to provide a recess and has a bottom region extended on a bottom of the recess. The first region is configured to cover the second region. In the etching method, a deposit of fluorocarbon is formed on the processing target object, and the first region is etched by irradiating ions of atoms of a rare gas toward the processing target object. Then, on the bottom region, a modified region is formed by supplying hydrogen ions. Subsequently, the deposit of fluorocarbon is formed on the processing target object, and the modified region is etched by irradiating ions of atoms of the rare gas toward the processing target object.