1. A method of making a semiconductor device, comprising: forming a first photoresist layer over an underlying layer; patterning the first photoresist layer into a first photoresist pattern, wherein the first photoresist pattern comprises a plurality of spaced apart first photoresist features located over the underlying layer; etching the underlying layer using the first photoresist pattern as a mask to form a plurality of first spaced apart features; removing the first photoresist pattern; forming a second photoresist layer over the plurality of first spaced apart features; patterning the second photoresist layer into a second photoresist pattern, wherein the second photoresist pattern comprises a plurality of second photoresist features covering edge portions of the plurality of first spaced apart features; etching exposed portions of the plurality of first spaced apart features using the second photoresist pattern as a mask, such that a plurality of spaced apart edge portions of the plurality of first spaced apart features remain; and removing the second photoresist pattern.