Patent ID: 9627206
Date: 2017-04-18
CPC Classifications: H01L

Claim:
1. A method comprising: forming a mandrel encircling a first opening and a second opening, wherein the first opening and the second opening are separated from each other by a first mandrel strip; etching a middle portion of the first mandrel strip to form a third opening connecting the first opening to the second opening, wherein the first mandrel strip comprises a first portion and a second portion remaining on opposite sides of the third opening; forming a blanket spacer layer over the mandrel; etching horizontal portions of the blanket spacer layer to form spacers, wherein the third opening is fully filled by the spacers, and the first opening and the second opening are narrowed by the spacers; etching the first portion and the second portion of the first mandrel strip to form a fifth opening and a sixth opening encircled by the mandrel and the spacers; using the mandrel and the spacers as an etching mask to etch a target layer, with trenches formed in the target layer; and filling the trenches with a filling material.