Fine line patterning methods

A pattern formation method, comprising:

• forming a hard mask layer over an underlying layer;
• forming a first hard mask pattern by patterning by using a lithography operation and an etching operation the hard mask layer;
• hardening a sidewall portion of the first hard mask pattern by using a directional implantation process;
• etching a portion of the first hard mask pattern by a directional etching process without covering the first hard mask pattern, leaving at least the hardened sidewall portion, resulting in a second hard mask pattern;
• and
• patterning the underlying layer using the second hard mask pattern as an etching mask.