US Patent 7811935 Isolation regions and their formation

A dielectric liner is formed in first and second trenches respectively in first and second portions of a substrate. A layer of material is formed overlying the dielectric liner so as to substantially concurrently substantially fill the first trench and partially fill the second trench. The layer of material is removed substantially concurrently from the first and second trenches to expose substantially all of the dielectric liner within the second trench and to form a plug of the material in the one or more first trenches. A second layer of dielectric material is formed substantially concurrently on the plug in the first trench and on the exposed portion of the dielectric liner in the second trench. The second layer of dielectric material substantially fills a portion of the first trench above the plug and the second trench.