Method of processing target object

A method of processing a target object having an etching target layer, an organic film provided on the etching target layer and a first mask provided on the organic film, the organic film including a first layer and a second layer, the first mask being provided on the first layer, the first layer being provided on the second layer, and the second layer being provided on the etching target layer, the method comprising:

• generating plasma of a first gas within a processing vessel of a plasma processing apparatus in which the target object is accommodated;
• etching the first layer with the plasma of the first gas and the first mask until the second layer is exposed;
• and conformally forming a protection film on a side surface of the first layer formed by the etching;
• generating plasma of a second gas within the processing vessel and removing the first mask with the plasma of the second gas;
• and
• after removing the first mask, etching the second layer by using the first layer and the protection film as a second mask,
• wherein the removing of the first mask is performed before the etching target layer is etched.