Patent ID: 7892943

Claim:
A method of forming a portion of a memory device, comprising: forming a dielectric liner overlying and in direct contact with a portion of a trench that extends into a substrate below an upper surface of the substrate; forming a first dielectric plug in the portion of a trench that extends into the substrate below the upper surface of the substrate so that an upper surface of the first dielectric plug is recessed below the upper surface of the substrate, the first dielectric plug comprising a layer of a first dielectric material overlying and in direct contact with the dielectric liner and a layer of a second dielectric material formed on the layer of the first dielectric material so that the upper surface of the first dielectric plug comprises an upper surface of the layer of the second dielectric material and a portion of the layer of the first dielectric material coplanar with the upper surface of the layer of the second dielectric material; and forming a second dielectric plug of a third dielectric material on the upper surface of the first dielectric plug so that the second dielectric plug extends from the upper surface of the first dielectric plug through another portion of the trench that extends above the upper surface of the substrate and that passes through a layer of a fourth dielectric material overlying the upper surface of the substrate and a conductive layer overlying the layer of fourth dielectric material, wherein the second dielectric plug contacts a portion of the layer of fourth dielectric material and a portion of the conductive layer.