Patent ID: 7332390

Claim:
A method for forming a semiconductor memory device, comprising: providing a semiconductor substrate, comprising a plurality of deep trenches, each comprising a first side, a second side opposite the first side and a third side between the first side and the second side, wherein the semiconductor substrates are defined to form a plurality of active areas, overlapping with a portion of the deep trench; forming a collar oxide layer in each deep trench, comprising a first side portion, a second side portion and a third side portion, adjacent to the first, second and third side of the deep trench respectively; forming a capacitor at a lower portion of each trench, comprising a bottom electrode, a top electrode and a dielectric layer between the bottom electrode and the top electrode, wherein top of the top electrode is between the top and bottom of the collar oxide layer; removing a portion of the second side portion of the collar oxide layer, wherein subsequent to the removing step, the top of the second side portion is at substantially the same level as top of the top electrode; forming a buried conductive layer overlying the top electrode and the second side portion; forming a buried strap in a portion of the semiconductor substrate adjacent to the second side of the deep trench, wherein the buried strap is adjacent to the buried conductive layer; and forming a transistor on a portion of the semiconductor substrate adjacent to the second side of the deep trench, wherein the transistor comprises a source, a drain and a gate, and the drain is electrically connected to the top electrode of the capacitor through the buried strap and the buried conductive layer.