Patent ID: 7269071

Claim:
A method for operating a memory, comprising: programming one or more vertical MOSFETs extending outwardly from a substrate and separated by trenches in a DRAM array in a reverse direction, wherein each MOSFET in the DRAM array includes a source region, a drain region, a channel region between the source and the drain regions, and a gate separated from the channel region by a gate insulator in the trenches, wherein the DRAM array includes a number of source lines formed in a bottom of the trenches between rows of the vertical MOSFETs and coupled to the source regions of each transistor along rows of the vertical MOSFETs, wherein along columns of the vertical MOSFETs the source region of each column adjacent vertical MOSFET couple to the source line in a shared trench, and wherein the DRAM array includes a number of bit lines coupled to the drain region along rows in the DRAM array, and wherein programming the one or more vertical MOSFETs in the reverse direction includes: applying a first voltage potential to a drain region of the vertical MOSFET; applying a second voltage potential to a source region of the vertical MOSFET; applying a gate potential to a gate of the vertical MOSFET; and wherein applying the first, second and gate potentials to the one or more vertical MOSFETs includes creating a hot electron injection into the gate insulator of the one or more MOSFETs adjacent to the source region such that the one or more vertical MOSFETs become programmed MOSFETs having one of a number of charge levels trapped in the gate insulator such that the programmed MOSFET operates at reduced drain source current in a forward direction.