| CPC H01L 23/5226 (2013.01) [H01L 21/31144 (2013.01); H01L 21/76807 (2013.01); H01L 21/76843 (2013.01); H01L 21/76877 (2013.01); H01L 23/5283 (2013.01)] | 9 Claims |

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1. A method for preparing a semiconductor device structure, comprising:
forming a first dielectric layer over and in contact with a top surface of a semiconductor substrate;
etching the first dielectric layer to form a first opening exposing the top surface of the semiconductor substrate, wherein the first opening is formed through the first dielectric layer from a top surface thereof to the top surface of the semiconductor substrate, such that a depth of the first opening is equal to a thickness of the first dielectric layer;
forming recesses by removing portions of the first dielectric layer at top corners of the first opening;
forming a first conductive plug in the first opening and the recesses, wherein a top surface of the first conductive plug is coplanar with a top surface of the first dielectric layer;
forming a second dielectric layer over the first dielectric layer to cover the top surface of the first conductive plug;
etching the second dielectric layer to form a second opening exposing the top surface of the first conductive plug; and
forming a second conductive plug in the second opening.
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