Method of etching and anti-reflection film using substituted hydrocarbon with halogen gas

A method of fabricating a semiconductor device, in which an anti-reflection film is etched with a resist taken as a mask, comprising:

• forming a device isolation oxide on a wafer substrate, said device isolation oxide having a total width and, in a head area of the oxide, a head;
• forming a polysilicon film on the device isolation oxide;
• forming an insulating film on the polysilicon film at a device isolation region of the semiconductor device coinciding with a location of the head;
• forming an anti-reflection film on said insulating film;
• forming a resist on said anti-reflection film and forming an initial opening portion in said resist;
• wherein a thickness of a portion of the resist and said anti-reflection film over the device isolation region is greater than over another region of the semiconductor device due to presence of said head;
• and
• forming a deepened opening portion by removing a portion, positioned at said initial opening portion of said resist, of said anti-reflection film by etching using an etching gas containing a substituted hydrocarbon with a halogen;
• wherein said deepened opening portion is disposed in said another region of the semiconductor device which is not over said head;
• wherein, in the removing step, a side wall blocking film is formed on walls of the deepened opening portion to allow anisotropic etching of the anti-reflection film;
• and
• wherein the wafer substrate is not etched during or proximate any of the stated steps.