Patent ID: 7923815

Claim:
A microelectronic element comprising: a semiconductor substrate; a first capacitor comprising a trench formed in the substrate, a first buried plate surrounding the trench, a node dielectric lining the trench, and a node disposed within the trench, and wherein the first buried plate has a first doping concentration; a second capacitor comprising a trench formed in the substrate, a second buried plate surrounding the trench, a node dielectric lining the trench, and a node disposed within the trench, and wherein the second buried plate has a second doping concentration; a first contact plug directly connected to the first buried plate for applying a first bias voltage to the first buried plate; a second contact plug directly connected to the second buried plate for applying a second bias voltage, different than the first bias voltage, to the second buried plate; and the semiconductor substrate having a non-uniform doping concentration wherein the first doping concentration differs from the second doping concentration by at least one order of magnitude.