An etching method is provided that includes the steps of supplying an etching gas containing a fluorocarbon (CF) based gas into a processing chamber, generating a plasma from the etching gas, and etching a silicon oxide film through a polysilicon mask using the plasma. The polysilicon film has a predetermined pattern and is arranged on the silicon oxide film. The silicon oxide film has at least one of a silicon content per unit volume, a fluorine content per unit volume, and a volume density that varies in a depth direction.