Resist feature and removable spacer pitch doubling patterning method for pillar structures

A method of making a semiconductor device includes forming a layer over a substrate, forming a plurality of spaced apart features of imagable material over the layer, forming sidewall spacers on the plurality of features and filling a space between a first sidewall spacer on a first feature and a second sidewall spacer on a second feature with a filler feature. The method also includes removing the sidewall spacers to leave the first feature, the filler feature and the second feature spaced apart from each other, and etching the layer using the first feature, the filler feature and the second feature as a mask.