In some methods, a first recess is etched in a selected region of a substrate. A first polymer liner is formed on sidewalls and a bottom surface of the first recess. A portion of the first polymer liner is removed from the bottom surface, and a remaining portion of the first polymer liner is left along the sidewalls. The first recess is deepened to establish a second recess while the remaining portion of the first polymer liner is left along the sidewalls. A first oxide liner is formed along the sidewalls and along sidewalls and a bottom surface of the second recess. A portion of the first oxide liner is removed from a bottom surface of the second recess, while a remaining portion of the first oxide liner is left on the sidewalls of the first recess and the sidewalls of the second recess.
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