In a processing method according to one exemplary embodiment, a first nitrified region of a workpiece is etched. The first nitrified region is provided on a first protrusion made of silicon. The workpiece further has a second protrusion, a second nitrified region, and an organic region. The second protrusion is made of silicon. The second nitrified region contains silicon and nitrogen and is provided on the second protrusion. The organic region covers the first and second protrusions and the first and second nitrified regions. In the processing method, the organic region is partially etched to expose the first nitrified region. Then, a silicon oxide film is formed to cover the surface of an intermediate product produced from the workpiece. Then, the silicon oxide film is etched to expose an upper surface of the first nitrified region. Then, the first nitrified region is isotropically etched.