Method of manufacturing a semiconductor device from which damage layers and native oxide films in connection holes have been removed

A semiconductor device manufacturing method comprising:

• dry-etching an insulating film formed on a conducting layer so as to make a connection hole in the insulating film to expose the conducting layer;
• supplying plasma excited from an oxidized gas onto the exposed conducting layer to dry-clean a damage layer produced in the connection hole;
• removing a product produced in the connection hole as a result of the dry cleaning by a wet process;
• etching an oxide film formed in the connection hole as a result of the wet process by a chemical dry process using a gas including either NF3 or HF;
• and
• removing a thermally decomposable reaction product produced as a result of the etching by heat treatment.