Abstract: A mechanism is provided for a thermally assisted magnetoresistive random access memory device (TAS-MRAM). A storage layer has an anisotropic axis, in which the storage layer is configured to store a state in off axis positions and on axis positions. The off axis positions are not aligned with the anisotropic axis. A tunnel barrier is disposed on top of the storage layer. A ferromagnetic sense layer is disposed on top of the tunnel barrier.

Abstract: The present invention is directed to an STT-MRAM device including a plurality of magnetic tunnel junction (MTJ) memory elements. Each of the memory elements comprises a magnetic free layer structure and a magnetic reference layer structure with an insulating tunnel junction layer interposed therebetween; and a magnetic fixed layer separated from the magnetic reference layer structure by an anti-ferromagnetic coupling layer.

Abstract: Method for writing to a MRAM cell including a magnetic tunnel junction including a first and second ferromagnetic layer, and a tunnel barrier layer; and a bipolar transistor in electrical connection with one end of the magnetic tunnel junction, the bipolar transistor being arranged for controlling the passing and polarity of a heating current in the magnetic tunnel junction. The method includes a sequence of writing steps, each writing step including passing the heating current in the magnetic tunnel junction such as to heat it to a high temperature threshold; and once the magnetic tunnel junction has reached the high temperature threshold, adjusting a second magnetization of the second ferromagnetic layer for writing a write data; wherein during one of the writing steps, the polarity of the heating current is reversed from one during the subsequent writing step. The method allows for an increased lifespan of the MRAM cell.

Abstract: A mechanism is provided for an integrated laminated magnetic device. A substrate and a multilayer stack structure form the device. The multilayer stack structure includes alternating magnetic layers and diode structures formed on the substrate. Each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by a diode structure.

Abstract: A method for determining an optimized write pattern for low write error rate operation of a spin torque magnetic random access memory. The method provides a way to optimize the write error rate without affecting the memory speed. The method comprises one or more write pulses. The pulses may be independent in amplitude, duration and shape. Various exemplary embodiments adjust the write pattern based on the memory operating conditions, for example, operating temperature.

Abstract: In an electronic device including a semiconductor memory, the semiconductor memory may include a unit storage cell including a variable resistor having a resistance value that is changed according to current flowing through both terminals of the variable resistor and a selection element that is electrically coupled to one terminal of the variable resistor, a unit current generation section that generates the current flowing through both terminals by using predetermined voltage according to a polarity of current data as compared with existing data, and a pad that receives the predetermined voltage from an exterior and allows the current flowing through both terminals to be measured from an exterior.

Abstract: Embodiments are directed to detecting a state of a memory element in a memory device, comprising: applying a pulse of a predetermined magnitude and duration to the memory element to induce a transition in the state of the memory element when a polarity of the pulse is opposite to the state, monitoring, by a device, a signal associated with the memory element to detect a presence or absence of a transition in the signal in an amount greater than a threshold, and determining the state of the memory element based on said monitoring.

Abstract: Select devices for memory cell applications and methods of forming the same are described herein. As an example, one or more non-ohmic select devices can include at least two tunnel barrier regions formed between a first metal material and a second metal material, and a third metal material formed between each of the respective at least two tunnel barrier regions. The non-ohmic select device is a two terminal select device that supports bi-directional current flow therethrough.

Abstract: An atomic-scale structure according to one embodiment has a net magnetic moment of zero or about zero, two or more stable magnetic states, and an array of atoms that has magnetic moments that alternate between adjacent magnetic atoms along one or more directions. Such structures may be used to store data at ultra-high densities. An antiferromagnetic nanostructure according to another embodiment includes multiple arrays each corresponding to a bit. Each array has at least eight antiferromagnetically coupled magnetic atoms. Each array has at least two readable magnetic states that are stable for at least one picosecond. Each array has a net magnetic moment of zero or about zero. No external stabilizing structure exerts influence over the arrays for stabilizing the arrays. Each array has 100 atoms or less along a longest dimension thereof.

Abstract: A Magnetoresistive Tunnel Junction (MTJ) includes a magnetic reference layer disposed between a first electrode and a resistive layer. The junction also includes a magnetic free layer disposed between the resistive layer and a second electrode. The surface area of the free layer is less than the surface area of the reference layer.

Abstract: An STT magnetic memory includes adjacent columns of STT magnetic memory elements having a top electrode and a bottom electrode. A shared bit line is coupled to the top electrode of the STT magnetic memory elements in at least two of the adjacent columns. The bottom electrodes of the STT magnetic memory elements of one of the adjacent columns are selectively coupled to one source line, and the bottom electrodes of the STT magnetic memory elements of another among the adjacent columns are selectively coupled to another source line.

Abstract: Memory sense amplifiers and memory verification methods are described. According to one aspect, a memory sense amplifier includes a first input coupled with a memory element of a memory cell, wherein the memory element has different memory states at different moments in time, a second input configured to receive a reference signal, modification circuitry configured to provide a data signal at the first input from the memory element having a plurality of different voltages corresponding to respective ones of different memory states of the memory cell at the different moments in time, and comparison circuitry coupled with the modification circuitry and configured to compare the data signal and the reference signal at the different moments in time and to provide an output signal indicative of the memory state of the memory cell at the different moments in time as a result of the comparison to implement a plurality of verify operations of the memory states of the memory cell at the different moments in time.

Abstract: In one embodiment, there is provided a non-volatile magnetic memory cell. The non-volatile magnetic memory cell comprises a switchable magnetic element; and a word line and a bit line to energize the switchable magnetic element; wherein at least one of the word line and the bit line comprises a magnetic sidewall that is discontinuous.

Abstract: A magnetoresistive element according to an embodiment includes: a first to third ferromagnetic layers, and a first nonmagnetic layer, the first and second ferromagnetic layers each having an axis of easy magnetization in a direction perpendicular to a film plane, the third ferromagnetic layer including a plurality of ferromagnetic oscillators generating rotating magnetic fields of different oscillation frequencies from one another. Spin-polarized electrons are injected into the first ferromagnetic layer and induce precession movements in the plurality of ferromagnetic oscillators of the third ferromagnetic layer by flowing a current between the first and third ferromagnetic layers, the rotating magnetic fields are generated by the precession movements and are applied to the first ferromagnetic layer, and at least one of the rotating magnetic fields assists a magnetization switching in the first ferromagnetic layer.

Abstract: A magnetic tunnel junction (MTJ) device is provided that includes a MTJ element and a control wire. The MTJ element includes a top ferromagnet layer formed of a first magnetic material, a tunneling layer, and a bottom ferromagnet layer formed of a second magnetic material. The tunneling layer is mounted between the top ferromagnet layer and the bottom ferromagnet layer. The control wire is configured to conduct a charge pulse. A direction of charge flow in the control wire extends substantially perpendicular to a magnetization direction of the top ferromagnet layer. The control wire is positioned sufficiently close to the top ferromagnet layer to reverse the magnetization direction of the top ferromagnet layer when the charge pulse flows therethrough while not reversing the magnetization direction of the bottom ferromagnet layer when the charge pulse flows therethrough.

Abstract: A magnetoresistive random access memory (MRAM) bit cell includes a first magnetic tunnel junction (MTJ) connected to a first data line. The MRAM bit cell further includes a second MTJ connected to a second data line. The MRAM bit cell further includes a pass gate assembly connected to the first MTJ and the second MTJ, wherein the pass gate assembly comprises a plurality of transistors, and each transistor of the plurality of transistors is configured to selectively connect the first MTJ and the second MTJ to a driving line.

Abstract: Some embodiments include methods of forming memory cells. Such methods can include forming a first electrode, a second electrode, and a memory element directly contacting the first and second electrodes. Forming the memory element can include forming a programmable portion of the memory element isolated from the first electrode by a first portion of the memory element and isolated from the second electrode by a second portion of the memory element. Other embodiments are described.

Abstract: An example magnetic recording device includes a magnetic recording section and a magnetization oscillator and a first nonmagnetic layer disposed between the magnetic recording section and the magnetization oscillator. The magnetic recording section includes a first ferromagnetic layer with a magnetization substantially fixed in a first direction; a second ferromagnetic layer with a variable magnetization direction; and a second nonmagnetic layer disposed between the first ferromagnetic layer and the second ferromagnetic layer. The magnetization oscillator includes a third ferromagnetic layer with a variable magnetization direction; a fourth ferromagnetic layer with a magnetization substantially fixed in a second direction; and a third nonmagnetic layer disposed between the third ferromagnetic layer and the fourth ferromagnetic layer.

Abstract: A nonvolatile memory comprising at least one ferromagnetic region having permittivity which changes from a first state to a second state of lower permittivity upon heating; at least one heater operatively associated with the at least one ferromagnetic region which selectively provides heat to the ferromagnetic region to change its permittivity; and a plurality of connectors operatively connected to the at least one heater and adapted to be connected to a current source that provides a current which causes the heater to change the at least one ferromagnetic region from a first state to a second state. Optionally, the memory is arranged as an array of memory cells. Optionally, each cell has a magnetic field sensor operatively associated therewith. Optionally, the nonvolatile memory is radiation hard. Also, a method of recording data by heating at least one ferromagnetic region to change its permittivity.

Abstract: Methods for determining memory cell states during a read operation using a detection scheme that reduces the area of detection circuitry for detecting the states of the memory cells by time multiplexing the use of portions of the detection circuitry are described. The read operation may include a precharge phase, a sensing phase, and a detection phase. In some embodiments, a first bit line and a second bit line may be precharged to a read voltage in parallel, and then sensing and/or detection of selected memory cells corresponding with the first bit line and the second bit line may be performed serially using the same detection circuitry by time multiplexing the use of the detection circuitry. In some cases, the time multiplexed detection circuitry may be used for detecting two or more states corresponding with two or more memory cells being sensed during a read operation.

Abstract: A method of forming a line of magnetic tunnel junctions includes forming magnetic recording material over a substrate, non-magnetic material over the recording material, and magnetic reference material over the non-magnetic material. The substrate has alternating outer regions of reactant source material and insulator material along at least one cross-section. The reference material is patterned into a longitudinally elongated line passing over the alternating outer regions. The recording material is subjected to a set of temperature and pressure conditions to react with the reactant of the reactant source material to form regions of the dielectric material which longitudinally alternate with the recording material along the line and to form magnetic tunnel junctions along the line which individually comprise the recording material, the non-magnetic material, and the reference material that are longitudinally between the dielectric material regions.

Abstract: A non-volatile semiconductor storage device according to each of the embodiments includes a cell array that includes a plurality of first wires extending in a first direction, a plurality of second wires extending in a second direction crossing the first direction, and a plurality of memory cells each provided at an intersection between each of the first wires and each of the second wires. Each memory cell includes a variable resistance film of which resistance varies depending on a state of a filament in a medium. Each cell array has a first portion at which a distance between the first wire and the second wire is minimized and a second portion at which a distance between the first wire and the second wire is larger than the first portion at the intersection between each of the first wires and each of the second wires.

Abstract: A nonvolatile memory element of the present invention comprises a first electrode (103), a second electrode (105), and a resistance variable layer (104) disposed between the first electrode (103) and the second electrode (104), a resistance value of the resistance variable layer varying reversibly according to an electric signal applied between the electrodes (103), (105), and the resistance variable layer (104) comprises at least a tantalum oxide, and is configured to satisfy 0<x<2.5 when the tantalum oxide is represented by TaOx.

Abstract: A magnetic device includes a magnetized polarizing layer, a free magnetic layer, and a reference layer. The free magnetic layer forms a first electrode and is separated from the magnetized polarizing layer by a first non-magnetic metal layer. The free magnetic layer has a magnetization vector having a first and second stable state. The reference layer forms a second electrode and is separated from the free-magnetic layer by a second non-magnetic layer. Unipolar current is sourced through the polarizing, free magnetic and reference layers. Switching of the magnetization vector of the free magnetic layer from the first stable state to the second state is initiated by application of a first unipolar current pulse, and switching of the magnetization vector of the free magnetic layer from the second stable state to the first stable state is initiated by application of a second unipolar current pulse.

Abstract: An embodiment includes a magnetic tunnel junction (MTJ) including a free magnetic layer, a fixed magnetic layer, and a tunnel barrier between the free and fixed layers; the tunnel barrier directly contacting a first side of the free layer; and an oxide layer directly contacting a second side of the free layer; wherein the tunnel barrier includes an oxide and has a first resistance-area (RA) product and the oxide layer has a second RA product that is lower than the first RA product. The MTJ may be included in a perpendicular spin torque transfer memory. The tunnel barrier and oxide layer form a memory having high stability with an RA product not substantively higher than a less stable memory having a MTJ with only a single oxide layer. Other embodiments are described herein.

Abstract: A word line driver circuit allows for dynamic selection of different word line voltages for selection and deselection of memory cells included in a resistive memory array in a manner that reduces circuit complexity, device count, and leakage currents.

Abstract: A magnetic memory according to an embodiment includes: a multilayer structure including a semiconductor layer and a first ferromagnetic layer; a first wiring line electrically connected to the semiconductor layer; a second wiring line electrically connected to the first ferromagnetic layer; and a voltage applying unit electrically connected between the first wiring line and the second wiring line to apply a first voltage between the semiconductor layer and the first ferromagnetic layer during a write operation, a magnetization direction of the first ferromagnetic layer being switchable by applying the first voltage.

Abstract: A resistance-based memory includes a two-diode access device. In a particular embodiment, a method includes biasing a bit line with a first voltage. The method further includes biasing the sense line with a second voltage. Biasing the bit line and biasing the sense line generates a current through a resistance-based memory element and through one of a first diode and a second diode. A cathode of the first diode is coupled to the bit line and an anode of the second diode is coupled to the sense line.

Abstract: The disclosed subject matter relates to a non-volatile memory bit cell (500 or 600) for solid-state data storage, including, e.g., an elongated magnetic element (102) or “dot”. For appropriate geometry and dimensions of the dot, a two-fold, energetically-degenerate micromagnetic configuration (100 or 200) can be stabilized. Such a stable configuration can consist of two magnetic vortices (1081, 1082) and a flower state region (110). Due to energy minimization, the flower state region can be off-center (relative to a minor axis (106)) and along the major axis (104) of the dot. An electrical current (302) flowing perpendicular to the plane at, or in proximity to, the dot center can, according to current polarity, switch the configuration or state of the dot between the two specular magnetically stable configurations (e.g., a write operation). Reading of the cell state can be accomplished by using the magnetoresistive effect.

Abstract: A magnetic memory cell including a piezoelectric material, and methods of operating the memory cell are provided. The memory cell includes a stack, and the piezoelectric material may be formed as a layer in the stack or adjacent the layers of the cell stack. The piezoelectric material may be used to induce a transient stress during programming of the memory cell to reduce the critical switching current of the memory cell.

Abstract: One embodiment describes a memory cell. The memory cell includes a phase hysteretic magnetic Josephson junction (PHMJJ) that is configured to store one of a first binary logic state corresponding to a binary logic-1 state and a second binary logic state corresponding to a binary logic-0 state in response to a write current and to generate a superconducting phase based on the stored digital state. The memory cell also includes at least one Josephson junction having a critical current that is based on the superconducting phase of the PHMJJ and being configured to provide an output corresponding to the stored digital state in response to a read current.

Abstract: According to one embodiment, a magnetoresistive memory device includes first and second bit lines, a memory cell, a power supply line, first and second transistors, and third and fourth transistors. The memory cell has first and second magnetoresistive elements and is connected between the first and second bit lines. The power supply line is connected between the first and second magnetoresistive elements. The first and second transistors have current paths inserted in the first and second bit lines, respectively, and have gate electrodes connected, respectively to the second and first bit lines provided on a side opposite to the memory cell. The third and fourth transistors are inserted in the first and second bit lines. Gate electrodes of the third and fourth transistors are cross-coupled, and the third and fourth transistors are controlled by current from the memory cell.

Abstract: Methods for determining memory cell states during a read operation using a detection scheme that reduces the area of detection circuitry for detecting the states of the memory cells by time multiplexing the use of portions of the detection circuitry are described. The read operation may include a precharge phase, a sensing phase, and a detection phase. In some embodiments, a first bit line and a second bit line may be precharged to a read voltage in parallel, and then sensing and/or detection of selected memory cells corresponding with the first bit line and the second bit line may be performed serially using the same detection circuitry by time multiplexing the use of the detection circuitry. In some cases, the time multiplexed detection circuitry may be used for detecting two or more states corresponding with two or more memory cells being sensed during a read operation.

Abstract: According to one embodiment, a memory device includes a memory cell, a sense amplifier, and a resistor. The sense amplifier includes a first input and a second input, outputs a signal in accordance with a difference between the first and second inputs, and is selectively coupled at a second input to the memory cell. The resistor is in a first path between the first input of the sense amplifier and a ground node.

Abstract: A one time programming (OTP) apparatus unit cell includes multiple magnetic tunnel junctions (MTJs) and a shared access transistor coupled between the multiple MTJs and a fixed potential. Each of the multiple MTJs in a unit cell can be coupled to separate programming circuitry and/or separate sense amplifier circuitry so that they can be individually programmed and/or individually sensed. A logical combination from the separate sense amplifiers can be generated as an output of the unit cell.

Abstract: A three-dimensional (3-D) memory stack and a method of formation thereof are described. The 3-D memory stack includes a number of vertically stacked memory devices. Each memory device includes one or more memory cells. Each of the memory cells can be formed on a conductive material. Each memory device further includes one or more selector elements each configured to couple a memory cell of the one or more memory cells to a respective bit line. None of the selector elements is configured as a diode or a transistor element.

Abstract: Provided is a tunnel magnetoresistive effect element such that a high TMR ratio and a low write current can be realized, and the thermal stability factor (E/kBT) of a recording layer and a pinned layer is increased while an increase in resistance of the element as a whole is suppressed, thus enabling a stable operation. On at least one of a recording layer 21 and a pinned layer 22 each comprising CoFeB, electrically conductive oxide layers 31 and 32 are disposed on a side opposite to a tunnel barrier layer 10.

Abstract: A magnetic storage element includes a magnetic nanowire. A cross-section of the magnetic nanowire has first and second visible outlines, the first visible outline has a first minimal point at which a distance from a virtual straight line becomes minimal, a second minimal point at which the distance from the virtual straight line becomes minimal, and a first maximal point at which the distance from the virtual straight line becomes longest between the first minimal point and the second minimal point, and an angle between a first straight line connecting the first minimal point and the second minimal point, and one of a second straight line connecting the first minimal point and the first maximal point and a third straight line connecting the second minimal point and the first maximal point is not smaller than four degrees and not larger than 30 degrees.

Abstract: A first write driver applies a first voltage above a fixed potential to a first terminal. A second write driver applies a second voltage that is higher above the fixed potential than the first voltage to a second terminal. There is at least one magnetic tunnel junction (MTJ) structure coupled at the first terminal at a first side to the first write driver and coupled at the second terminal at a second side to the second write driver. The first side of the MTJ structure receives the first voltage and the second side of the MTJ structure receives a ground voltage to change from a first state to a second state. The second side of the MTJ structure receives the second voltage and the first side of the MTJ structure receives the ground voltage to change from the second state to the first state.

Abstract: A method and system provide a magnetic junction. A free layer, a symmetry filter, and a pinned layer are provided. The free layer has a magnetic moment switchable between stable states when a write current is passed through the magnetic junction. The symmetry filter transmits charge carriers having a first symmetry with higher probability than charge carriers having another symmetry. The symmetry filter resides between the free layer and the pinned layer. The free layer and/or the pinned layer lies in a plane, has the charge carriers of the first symmetry in a spin channel at a Fermi level, lacks the charge carriers of the first symmetry at the Fermi level in another spin channel, and has a nonzero magnetic moment component perpendicular to the plane. The free layer and/or the pinned layer and the symmetry filter has at least one lattice mismatch of less than seven percent.

Abstract: A semiconductor device, including: a first transistor sharing a first diffusion with a second transistor; a third transistor sharing a second diffusion with the second transistor; and at least one programmable resistor; wherein the at least one programmable resistor is connected to the first diffusion and the second diffusion, wherein the at least one programmable resistor includes one of the following: memristor, transition metal oxides, polymeric memristor, ferroelectric memristor, spintronic memristor, spin transfer torque, phase-change structure, programmable metallization structure, conductive-bridging structure, magnetoresistive structure, chalcogenide structure.

Abstract: Embodiments are directed to detecting a state of a memory element in a memory device, comprising: applying a pulse of a predetermined magnitude and duration to the memory element to induce a transition in the state of the memory element when a polarity of the pulse is opposite to the state, monitoring, by a device, a signal associated with the memory element to detect a presence or absence of a transition in the signal in an amount greater than a threshold, and determining the state of the memory element based on said monitoring.

Abstract: A nonvolatile random access memory device includes a plurality of memory cells configured to store data therein, a plurality of reference cells separate from the memory cells, the reference cells each configured to output a corresponding reference cell signal, and a read/write circuit. The read/write circuit is configured to generate from the reference cell signals a reference signal which is variable to have a plurality of different reference levels. The read/write circuit is further configured to identify, in response to the reference signal, a logic state among a first logic state and a second logic state for each of one or more selected memory cells, and to output read data corresponding to the identified logic state.

Abstract: A nano-magnetic element array having a conductive line adjacent to a group of nano-magnetic elements and a multi-level current driver connected to an input node on the conductive line. The current driver is controlled by a pair of voltage clock signals and a voltage reference so as to selectively change the current amount at the input node between a first level that erases the state of the elements, a second level that switches the state of the elements and a third level that maintains the state of the elements. The current driver is further configured so that the transition from the second to the third level is gradual. Optionally, a bias generator can selectively adjust the voltage reference and thereby, the current amount at the input node. Also, optionally, the same voltage clock signal and voltage reference lines can be used to control multiple multi-level current drivers within the array.

Abstract: This disclosure relates to generating a reference current for a memory device. In one aspect, a non-volatile memory device, such as a phase change memory device, can determine a value of a data digit, such as a bit, stored in a non-volatile memory cell based at least partly on the reference current. The reference current can be generated by mirroring a current at a node that is biased by a voltage bias. A configurable resistance circuit can have a resistance that is configurable. The resistance of the configurable resistance circuit can be in series between the node and a resistive non-volatile memory element. In some embodiments, a plurality of non-volatile memory elements can each be electrically connected in series between the resistance of the configurable resistance circuit and a corresponding selector.

Abstract: A method of forming a magnetic memory includes providing a layer stack comprising a plurality of magnetic layers and a plurality of electrically conducting layers on a base portion of a substrate; forming a first mask feature on an outer surface of the layer stack above a first protected region and a second mask feature on the outer surface of the layer stack above a second protected region, the first mask feature and second mask feature defining an exposed region of the layer stack in portions of the layer stack therebetween; and directing ions towards exposed the region of the layer stack in an ion exposure that is effective to magnetically isolate the first protected region from the second protected region and to electrically isolate the first protected region from the second protected region without removal of the exposed region of the layer stack.

Abstract: An oscillator using spin transfer torque includes i) a pinned magnetic layer having a fixed magnetization direction, ii) a non-magnetic layer located on the pinned magnetic layer, and iii) a free magnetic layer located on the non-magnetic layer. The pinned magnetic layer includes i) a first part of the fixed magnetic layer and ii) a second part of the fixed magnetic layer located thereon. The first part of the fixed magnetic layer includes i) a first interface in contact with the second part of the fixed magnetic layer and ii) a second surface exposed to an outside while surrounding the first interface.

Abstract: A hybrid non-volatile memory device includes a non-volatile random access memory (NVRAM) having an array of magnetic memory elements, the NVRAM being bit-accessible. The hybrid non-volatile device further includes a non-volatile page-mode memory (PMM) made of resistive memory and organized into pages, the non-volatile PMM being page-accessible. Further included in the hybrid non-volatile memory device is a direct memory access (DMA) engine that is coupled to the NVRAM and the non-volatile PMM and transfers data between the NVRAM and the non-volatile PMM during a DMA operation.

Abstract: Provided is a nonvolatile memory device using a resistance material and a method of driving the nonvolatile memory device. The nonvolatile memory device comprises a resistive memory cell which stores multiple bits; a sensing node; a clamping unit coupled between the resistive memory cell and the sensing node and provides a clamping bias to the resistive memory cell; a compensation unit which provides a compensation current to the sensing node; a sense amplifier coupled to the sensing node and senses a change in a level of the sensing node; and an encoder which codes an output value of the sense amplifier in response to a first clock signal. The clamping bias varies over time. The compensation current is constant during a read period.

Abstract: A nonvolatile semiconductor storage device includes: a plurality of stacked units juxtaposed on a major surface of a substrate, each stacked unit aligning in a first direction parallel to the major surface of the substrate; and a gate electrode aligning parallel to the major surface in a second direction non-parallel to the first direction. Each of the plurality of stacked units includes a plurality of stacked semiconductor layers via an insulating layer. The plurality of stacked units are juxtaposed so that the spacings between adjacent stacked units are alternately a first spacing and a second spacing larger than the first spacing. The second spacing is provided at a periodic interval four times a size of a half pitch F of the bit line. The gate electrode includes a protruding portion that enters into a gap of the second spacing between the stacked units.