According to one embodiment, a method for manufacturing a memory system that has memory cells with a variable resistance element and a switching element connected between a first wire and second wire, includes forming the variable resistance elements in the memory system in a low resistance state or a high resistance state, and then bringing each of the variable resistance elements into the low resistance state before performing either of a read operation or a write operation by performing an external initialization process that is different from the read operation and the write operation. In some examples, the variable resistance element can be a magnetoresistance type element and the external initialization process may be exposing the memory cells to an external magnetic field.

Numerous embodiments of circuitry for a set-while-verify operation and a reset-while verify operation for resistive random access memory cells are disclosed. In one embodiment, a set-while-verify circuit for performing a set operation on a selected RRAM cell in the array applies a combination of voltages or current to a bit line, word line, and source line associated with the selected RRAM cell and stops said applying when the set operation is complete. In another embodiment, a reset-while-verify circuit for performing a reset operation on a selected RRAM cell in the array applies a combination of voltages or current to a bit line, word line, and source line associated with the selected RRAM cell and stops said applying when the reset operation is complete.

An electroforming process for a resistive memory of a memory device including a memory controller, an encoder computing an inversion-invariant linear error correction code, and a write device connected directly to the encoder. An electroforming device performing electroforming through write operations to such a resistive memory and to a method for checking a write operation.

A semiconductor memory device includes programmable resistance memory cells and a controller which applies a forming pulse to first and second groups of the programmable resistance memory cells for inducing a change in the first group from an initial resistance range to an intermediate resistance range, and for inducing the second group having a resistance outside the intermediate range. When a forming rate is lower than a first forming threshold rate, the controller adjusts the forming pulse until the forming rate is higher than the first forming threshold rate. When a forming rate is higher than the first forming threshold rate but lower than a second forming threshold rate, the controller adjusts the forming pulse until the forming rate is higher than the second forming threshold rate. The controller applies a programming pulse to the first and second groups and generates a chip ID of the semiconductor memory device.

A data-write device includes a write driver that causes a current to flow through a current path including an MTJ element or the other current path including the MTJ element in accordance with writing data to be written, thereby writing the write data into the MTJ element, a write completion detector which monitors the voltage at a first connection node or a second connection node in accordance with the write data after the writing of the write data into the MTJ element starts, detects the completion of writing of the write data based on the voltage at either node, and supplies a write completion signal indicating the completion of data write, and a write controller that terminates the writing of the write data into the MTJ element in response to the write completion signal supplied from the write completion detector.

Various embodiments provide methods for configuring a phase-change random-access memory (PCRAM) structures, such as PCRAM operating in a single-level-cell (SLC) mode or a multi-level-cell (MLC) mode. Various embodiments may support a PCRAM structure being operating in a SLC mode for lower power and a MLC mode for lower variability. Various embodiments may support a PCRAM structure being operating in a SLC mode or a MLC mode based at least in part on an error tolerance for a neural network layer.

A process is provided to trim PCRAM cells to have consistent programming curves. Initial programming curves of PCRAM cells are measured. A target programming curve is set up for the PCRAM cells. Each PCRAM cell is then modulated individually to meet the target programming curve.

A resistive random access memory (RRAM) circuit and related method limits current, or ramp voltage, applied to a source line or bitline of an RRAM array. The RRAM array has one or more source lines and one or more bitlines. A control circuit sets an RRAM cell to a low resistance state in a set operation, and resets the RRAM cell to a high resistance state in a reset operation. A voltage applied to a bitline or source line is ramped during a first time interval, held to a maximum voltage value during a second interval, and ceased after the second time interval.

Technology is described for selecting a group of reversible-resistance memory cells in which to store data based on information regarding switching the reversible-resistance memory cells from a first resistance state in which the reversible-resistance memory cells are in immediately after fabrication to a second resistance state for the first time after fabrication. Information regarding switching the reversible-resistance memory cells from the first resistance state to the second resistance state for the first time after fabrication may provide insight into factors including, but not limited to, endurance and data retention. In one aspect, a control circuit is configured to select a group of reversible-resistance memory cells in which to store data based on both the difficulty in switching from the first resistance state to the second resistance state for the first time after fabrication and a temperature of the data to be stored in the memory system.

A nonvolatile memory device comprises: resistive memory cells each of which takes either a variable state or an initial state, the resistive memory cells including at least one resistive memory cell in the initial state; and a read circuit that comprising a resistance detection circuit that obtains resistance value information of the at least one resistive memory cell, and a data generation circuit that generates digital data corresponding to the resistance value information. The resistance detection circuit applies a second read voltage to the at least one resistive memory cell to obtain the resistance value information. The second read voltage is larger than a first read voltage and smaller than a voltage of a forming pulse that is an electrical stress for changing from the initial state to the variable state. The first read voltage is for reading a resistive memory cell in the variable state.