Sidewall assisted process for wide and narrow line formation

A method of forming narrow and wide lines includes forming mandrels separated by wider gaps and narrower gaps, forming sidewall spacers on sides of the gaps, and then removing the mandrels. Subsequent anisotropic etching extends through an underlying mask layer at locations between sidewall spacers that were formed in wider gaps, to thereby separate narrow line portions of the mask layer, without extending through the mask layer at locations between sidewall spacers that were formed in narrower gaps, thereby leaving wide line portions of the mask layer under the second sidewall spacers.