Patent ID: 8822321

Claim:
A pattern forming method comprising: forming a first mask film above a processing target; forming an opening pattern in a predetermined area of the first mask film; conformally forming a second mask film of a material different from that of the first mask film above the processing target above which the opening pattern is formed; performing etch-back of the second mask film until an upper surface of the first mask film is exposed so that the second mask film remains on a side surface of the first mask film; forming a third mask film formed of the same material as the first mask film above the processing target after the second mask film remains on the side surface of the first mask film; planarizing an upper surface of the third mask film by using the second mask film as a stopper; forming line-and-space-shaped first core patterns, that are made of a first core film and in which widths of line patterns have smaller than a width of the second mask film remaining on the side surface of the first mask film, in an area other than an area forming the opening pattern of the processing target after the third mask film is planarized; conformally forming a first sidewall film above the processing target above which the first core patterns are formed; performing etch-back of the first sidewall film so that upper surfaces of the first core patterns are exposed; forming first sidewall patterns made of the first sidewall film by removing the first core patterns; forming mask patterns by etching the first mask film and the third mask film using the first sidewall patterns; and patterning the processing target by using the second mask film and the mask patterns as masks.