A semiconductor memory device includes a memory cell unit with a plurality of electrically rewritable memory cells connected in series, two ends thereof being coupled to a data transfer line and a reference potential line via select transistors, respectively, wherein the device has a data read mode defined as to detect a read current flowing between the data transfer line and the reference potential line, and judge data of a selected memory cell in the memory cell unit under the condition of: applying a read voltage to the selected memory cell, the read voltage being set to turn on or off the selected memory cell in accordance with data thereof; applying a pass voltage to remaining unselected memory cells, the pass voltage being set to turn on the remaining unselected memory cells without regard to data thereof; and making the select transistors on, and wherein in the data read mode, the more unselected memory cell or cells located on the source side of the selected memory cell, the higher the pass voltage applied to the unselected memory cell or cells located on the source side of the selected memory cell.
Nonvolatile evaluation memory cells are programmed to be a plurality of different values in advance, respectively. An internal voltage generating circuit can change the value of an internal voltage according to adjusting signals. To make the internal voltage close to its expected value, a voltage adjusting circuit outputs adjusting signals in accordance with cell currents that flow through the evaluation memory cells, respectively, in a read operation on the evaluation memory cells. As a result, the interval voltage that is shifted from its expected value due to variations in manufacturing conditions can automatically be set to the expected value by using the adjusting signals. Since an internal circuit operates on a correct internal voltage, operation margins can be increased. The yield of a nonvolatile semiconductor memory can thus be increased.
A method and apparatus for multiplexing various voltage magnitudes onto the address line of a memory cell. An address line voltage generator applies complex analog voltage magnitudes to a memory cell address line during Power On Reset (POR) to insure proper memory cell initialization during power up. Once initialized, read and write address select signals are level shifted to be equal to or greater than the read and write voltage magnitudes applied to the memory cell address line to ensure proper operation.
An integrated circuit comprises a resistive memory cell, at least one reference cell, a first device configured to apply a predetermined read voltage to the resistive memory cell and a second device configured to apply the predetermined read voltage to the reference cell. The resistive memory cell can be switched between a highly resistive memory state and at least one lowly resistive memory state. The reference cell comprises a resistance value representing a reference state. The first device generates the read voltage for a first resistance range, the first resistance range comprising the memory states of the resistive memory cell. The second device generates the read voltage for a second resistance range, the second resistance range being smaller in comparison to the first resistance range and comprising the reference state of the reference cell.
A system for reducing or removing a form of read disturb in a non-volatile storage device. One embodiment seeks to prevent read disturb by eliminating or minimizing boosting of the channel of the memory elements. For example, one implementation prevents or reduces boosting of the source side of the NAND string channel during a read process. Because the source side of the NAND string channel is not boosted, at least one form of read disturb is minimized or does not occur.
Unselected groups of non-volatile storage elements are boosted during programming to reduce or eliminate program disturb for targeted, but unselected memory cells connected to a selected word line. Prior to applying a program voltage to the selected word line and boosting the unselected groups, the unselected groups are pre-charged to further reduce or eliminate program disturb by providing a larger boosted potential for the unselected groups. During pre-charging, one or more pre-charge enable signals are provided at higher voltages for certain memory cells that may have undergone partial programming.
