Methods, systems, and devices for restoring memory cell threshold voltages are described. A memory device may perform a write operation on a memory cell during which a logic state is stored at the memory cell. Upon detecting satisfaction of a condition, the memory device may perform a read refresh operation on the memory cell during which the threshold voltage of the memory cell may be modified. In some cases, the duration of the read refresh operation may be longer than the duration of a read operation performed by the memory device on the memory cell or on a different memory cell.

An example apparatus can include a memory array and a memory controller. The memory array can include a first portion including a first plurality of memory cells. The memory array can further include a second portion including a second plurality of memory cells. The memory controller can be coupled to the first portion and the second portion. The memory controller can be configured to operate the first plurality of memory cells for short-term memory operations. The memory controller can be further configured to operate the second plurality of memory cells for long-term memory operations.

A variable resistive memory device includes a memory cell, a first current-applying block, a second current-applying block and a mode setting circuit. The memory cell includes a first electrode, a second electrode, and a memory layer, the memory layer interposed between the first electrode and the second electrode. The first current-applying block is configured to flow a first current to the first electrode that flows from the first electrode to the second electrode. The second current-applying block is configured to flow a second current to the second electrode that flows from the second electrode to the first electrode. The mode setting circuit is configured to selectively provide any one of the first electrode of the first current-applying block and the second electrode of the second current-applying block with a first voltage. When the memory cell is selected, the selected current-applying block, among the first current-applying block and the second current-applying block, is driven. When the first current-applying block is selected, a second voltage is applied to the second electrode. When the second current-applying block is selected, the second voltage is applied to the first electrode. The first voltage has a voltage level by a threshold voltage higher than the second voltage.

A non-volatile memory device is configured for in-memory computation of layers of a neural network by storing weight values as conductance values in memory cells formed of a series combination of a threshold switching selector, such as an ovonic threshold switch, and a programmable resistive element, such as a ReRAM element. By scaling the input voltages (representing inputs for the layer of the neural network) relative to the threshold values of the threshold switching selectors, dropout for inputs can be implemented to reduce overfitting by the neural network.

A memory device includes a cell region including a plurality of word lines, a plurality of bit lines, and a plurality of memory cells connected to the plurality of word lines and the plurality of bit lines disposed therein, where each of the plurality of memory cells includes a switch element and a memory element connected to each other in series between a corresponding word line and a corresponding bit line, and a peripheral circuit region including a control logic configured to, when a read command for a selected memory cell among the memory cells is received from an external controller, input a pre-voltage to the selected memory cell before reading data of the selected memory cell. The control logic is configured to determine a level of the pre-voltage with reference to an elapsed time after programming of the selected memory cell.

A memory circuit configured to perform multiply-accumulate (MAC) operations for performance of an artificial neural network includes a series of synapse cells arranged in a cross-bar array. Each cell includes a memory transistor connected in series with a memristor. The memory circuit also includes input lines connected to the source terminal of the memory transistor in each cell, output lines connected to an output terminal of the memristor in each cell, and programming lines coupled to a gate terminal of the memory transistor in each cell. The memristor of each cell is configured to store a conductance value representative of a synaptic weight of a synapse connected to a neuron in the artificial neural network, and the memory transistor of each cell is configured to store a threshold voltage representative of a synaptic importance value of the synapse connected to the neuron in the artificial neural network.

The present invention is directed to a magnetic memory cell including a magnetic tunnel junction (MTJ) memory element and a two-terminal bidirectional selector coupled in series between two conductive lines. The MTJ memory element includes a magnetic free layer, a magnetic reference layer, and an insulating tunnel junction layer interposed therebetween. The two-terminal bidirectional selector includes bottom and top electrodes, first and third volatile switching layers interposed between the bottom and top electrodes, and a second volatile switching layer interposed between the first and third volatile switching layers. The bottom and top electrodes each independently include one of titanium nitride or iridium. The first and third volatile switching layers each include tantalum oxide and silver. The second volatile switching layer includes hafnium oxide and has a higher electrical resistance than the first and third volatile switching layers.

Disclosed herein is a memory cell. The memory cell may act both as a combined selector device and memory element. The memory cell may be programmed by applying write pulses having different polarities. Different polarities of the write pulses may program different logic states into the memory cell. The memory cell may be read by read pulses all having the same polarity. The logic state of the memory cell may be detected by observing different threshold voltages when the read pulses are applied. The different threshold voltages may be responsive to the different polarities of the write pulses.

Methods, systems, and devices for programming techniques for polarity-based memory cells are described. A memory device may use a first type of write operation to program one or more memory cells to a first state and a second type of write operation to program one or more memory cells to a second state. Additionally or alternatively, a memory device may first attempt to use the first type of write operation to program one or more memory cells, and then may use the second type of write operation if the first attempt is unsuccessful.

An example apparatus can include a memory array and a memory controller. The memory array can include a first portion including a first plurality of memory cells. The memory array can further include a second portion including a second plurality of memory cells. The memory controller can be coupled to the first portion and the second portion. The memory controller can be configured to operate the first plurality of memory cells for short-term memory operations. The memory controller can be further configured to operate the second plurality of memory cells for long-term memory operations.