Localized array threshold voltage implant to enhance charge storage within DRAM memory cells

摘要

A DRAM device having improved charge storage capabilities and methods for providing the same. The device includes an array portion having a plurality of memory cells extending from a semiconductor substrate. Each cell includes a storage element for storing a quantity of charge indicative of the state of the memory cell and a valve element that inhibits the quantity of charge from changing during quiescent periods. The storage elements are disposed adjacent a plurality of storage regions of the substrate and the valve elements are disposed adjacent a plurality of valve regions of the substrate. A plurality of dopant atoms are selectively implanted into the array portion so as to increase a threshold voltage which is required to develop a conducting channel through the valve region. The dopant atoms are disposed mainly throughout the valve regions of the substrate and are substantially absent from the storage regions. Consequently, the increased threshold voltage results in a reduced subthreshold leakage current flowing through the valve region. Furthermore, the reduced dopant concentration within the storage regions results in a reduced junction leakage current flowing through the substrate that bypasses the valve region.