US Patent 7737480 Semiconductor memory device and manufacturing method thereof

A semiconductor memory device includes: a transistor formed in a substrate; a capacitor formed above one of source/drain regions of the transistor; a bit line formed above the substrate and extending in the gate length direction of the transistor; a first conductive plug connecting one of the source/drain regions and the capacitor; a second conductive plug connected to the other source/drain region that is not connected to the first conductive plug; and a third conductive plug formed on the second conductive plug and connected to the bit line. The central axis of the third conductive plug is displaced from the central axis of the second conductive plug in the gate width direction of the transistor.