A memory device may include a substrate having conductivity regions and a channel region. A first voltage line may be arranged over the channel region. Second, third, and fourth voltage lines may each be electrically coupled to a conductivity region. Resistive units may be arranged between the third voltage line and the conductivity region electrically coupled to the third voltage line, and between the fourth voltage line and the conductivity region electrically coupled to the fourth voltage line. A resistance adjusting element may have at least a portion arranged between one of the resistive units and one of the conductivity regions. An amount of the resistance adjusting element between the first resistive unit and the conductivity region electrically coupled to the third voltage line may be different from that between the second resistive unit and the conductivity region electrically coupled to the fourth voltage line.

Three-dimensional (3D) memory devices with 3D phase-change memory (PCM) and methods for forming and operating the 3D memory devices are disclosed. In an example, a 3D memory device includes a first semiconductor structure including an array of NAND memory cells, and a first bonding layer including first bonding contacts. The 3D memory device also further includes a second semiconductor structure including a second bonding layer including second bonding contacts, a semiconductor layer and a peripheral circuit and an array of PCM cells between the second bonding layer and the semiconductor layer. The 3D memory device further includes a bonding interface between the first and second bonding layers. The first bonding contacts are in contact with the second bonding contacts at the bonding interface.

Disclosed herein are related to a circuit and a method of reading or sensing multiple bits of data stored by a multi-level cell. In one aspect, a first reference circuit is selected from a first set of reference circuits, and a second reference circuit is selected from a second set of reference circuits. Based at least in part on the first reference circuit and the second reference circuit, one or more bits of multiple bits of data stored by a multi-level cell can be determined. According to the determined one or more bits, a third reference circuit from the first set of reference circuits and a fourth reference circuit from the second set of reference circuits can be selected. Based at least in part on the third reference circuit and the fourth reference circuit, additional one or more bits of the multiple bits of data stored by the multi-level cell can be determined.

Examples may include techniques to implement a SET write operation to a selected memory cell include in a memory array. Examples include selecting the memory cell that includes phase change material and applying various currents over various periods of time during a nucleation stage and a crystal growth stage to cause the memory cell to be in a SET logical state.

According to some embodiments of the present invention a phase change device (PCD) has a first and second semiconductor layer. The first semiconductor layer made of a first semiconductor material and has a first semiconductor thickness, a first interface surface, and a first electrode surface. The first interface surface and first electrode surface are on opposite sides of the first semiconductor layer. The first semiconductor material can transition between a first amorphous state and a first crystalline state at one or more first conditions. The second semiconductor layer is made of a second semiconductor material and has a second semiconductor thickness, a second interface surface, and a second electrode surface. The second interface surface and second electrode surface are on opposite sides of the second semiconductor layer. The first interface surface and the second interface surface are in electrical, physical, and chemical contact with one another at an interface. The second semiconductor material can transition between a second amorphous state and a second crystalline state at one or more second conditions. A first electrode in physical and electrical contact with the first electrode surface of the first semiconductor layer and a second electrode in physical and electrical contact with the second electrode surface of the second semiconductor layer. The first conditions and second conditions are different. Therefore, in some embodiments, the first and second semiconductor materials can be in different amorphous and/or crystalline states. The layers can have split amorphous/crystalline states. By controlling how the layers are split, the PCD can be in different resistive states.

A multi-level cell (MLC) one-selector-one-resistor (1S1R) three-dimensional (3D) cross-point memory system includes at least one MLC 1S1R structure including a stacked arrangement of a phase change memory (PCM) cell and a threshold switch selector. An electrically conductive bit line is in electrical communication with the OTS selector, and an electrically conductive word line is in electrical communication with the PCM cell. A controller is in electrical communication with the bit line and the word line. The controller is configured to select at least one voltage pulse from a group of different voltage pulses comprising a read pulse, a partial set pulse, a set pulse, a partial reset pulse, and a reset pulse, and configured to deliver the selected at least one voltage pulse to the at least one MLC 1S1R structure.

Methods, systems, and devices related to auto-referenced memory cell read techniques are described. The auto-referenced read may encode user data to include a predetermined number of bits having a first logic state prior to storing the user data in memory cells. The auto-referenced read may store a total number of bits of the user data having a first logic state in a separate set of memory cells. Subsequently, reading the user data may be carried out by applying a read voltage to the memory cells storing the user data while monitoring a series of switching events by activating a subset of the memory cells having the first logic state. During the read operation, the auto-referenced read may compare the number of activated memory cells to either the predetermined number or the total number to determine whether all the bits having the first logic state has been detected. When the number of activated memory cells matches either the predetermined number or the total number, the auto-referenced read may determine that the memory cells that have been activated correspond to the first logic state.

A phase change memory (PCM) cell comprises a first electrode comprised of a first electrically conductive material, a second electrode comprised of a second electrically conductive material, a first phase change layer positioned between the first electrode and the second electrode and being comprised of a first phase change material, and a second phase change layer positioned between the first electrode and the second electrode and being comprised of a second phase change material. The first phase change material has a first resistivity, the second phase change material has a second resistivity, and wherein the first resistivity is at least two times the second resistivity.

In some embodiments, the present disclosure relates a phase change random access memory device that includes a phase change material (PCM) layer disposed between bottom and top electrodes. A controller circuit is coupled to the bottom and top electrodes and is configured to perform a first reset operation by applying a signal at a first amplitude across the PCM layer for a first time period and decreasing the signal from the first amplitude to a second amplitude for a second time period; and to perform a second reset operation by applying the signal at a third amplitude across the PCM layer for a third time period and decreasing the signal from the third amplitude to a fourth amplitude for a fourth time period greater than the second time period. After the fourth time period, the PCM layer has a percent crystallinity greater than the PCM layer after the second time period.

Embodiments of semiconductor devices and fabrication methods thereof are disclosed. In an example, a semiconductor device includes a first semiconductor structure including a processor, an array of static random-access memory (SRAM) cells, and a first bonding layer including a plurality of first bonding contacts. The semiconductor device also includes a second semiconductor structure including an array of NAND memory cells and a second bonding layer including a plurality of second bonding contacts. The semiconductor device further includes a bonding interface between the first bonding layer and the second bonding layer. The first bonding contacts are in contact with the second bonding contacts at the bonding interface.