Method of fabricating semiconductor device including forming a protective layer and removing after etching a trench

A method of fabricating a semiconductor device compromising:

• dry-etching an exposed portion of a surface of a semiconductor substrate, the exposed portion being not covered with an etching mask that covers a remaining portion of the surface of the semiconductor substrate, and forming a trench that includes a trench bottom and a trench sidewall, the trench bottom being defined by a bottom portion of the dry-etched surface, the trench sidewall being defined by a sidewall portion of the dry-etched surface;
• a trench etching step including sub steps of:
• depositing a fluorocarbon protection film on the trench bottom and the trench sidewall, and
• dry-etching the protection film deposed on the bottom of the trench so as to expose at least a portion of the semiconductor substrate, and further dry-etching the exposed portion of the semiconductor substrate;
• partially decomposing the protection film on the trench sidewall by heating the semiconductor substrate at a predetermined temperature following the trench etching step;
• and
• removing the partially-decomposed protection film from the trench sidewall by performing plasma ashing on the heated semiconductor.