1. A method of making a device, comprising: forming at least one device layer over a substrate; forming a plurality of spaced apart first features over the device layer, wherein each three adjacent first features form an equilateral triangle; forming sidewall spacers on the first features; filling a space between the sidewall spacers with a plurality of filler features; selectively removing the sidewall spacers; and etching the at least one device layer using at least the plurality of filler features as a mask.