Patent ID: 12236998

DETAILED DESCRIPTION

Hereinafter, example embodiments of the present disclosure will be described with reference to the accompanying drawings.

FIG.1is a schematic block diagram illustrating a semiconductor device according to example embodiments of the present disclosure.

Referring toFIG.1, a semiconductor device10may be a storage device based on a semiconductor element. The semiconductor device10may be a random access memory (RAM) device such as dynamic random access memory (DRAM), synchronous DRAM (SDRAM), static RAM (SRAM), double date rate SDRAM (DDR SDRAM), DDR2 SDRAM, DDR3 SDRAM, phase-change RAM (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM), or the like. The semiconductor device10may store data received through a data signal DQ (not shown) or output data through the data signal DQ, in response to an address signal ADDR (not shown) and a control command signal CMD (not shown) received from an external host (for example, a central processing unit (CPU), an application processor (AP), or a system on a chip (SoC). The semiconductor device10may include a memory cell array20and a peripheral circuit30, and the peripheral circuit30may include a word line driving circuit31, a control logic32, a sense amplifier circuit33, a column decoder34, and the like.

The memory cell array20may include a plurality of memory cells, and the plurality of memory cells may be connected to the word line driving circuit31through a plurality of word lines WL, and may be connected to the sense amplifier circuit33through a plurality of bit lines BL. As used herein, when two or more elements having electrical functionality are described as being connected, it may refer to the two or more elements being electrically connected, unless the context indicates otherwise. Each of the plurality of memory cells may be positioned at a respective point at which the plurality of word lines WL and the plurality of bit lines BL intersect. The plurality of memory cells may be arranged in a matrix form in the memory cell array20, and each of the plurality of memory cells may include at least one memory element for storing data. For example, when the semiconductor device10is a DRAM, each of the plurality of memory cells may include a switch element and a cell capacitor.

The control logic32may receive an address signal and a control command signal from the external host. The address signal may include a row address indicating a row in the memory cell array20and a column address indicating a column in the memory cell array20. For example, the word line driving circuit31may select at least one of the plurality of word lines WL with reference to the row address, and the column decoder34may select at least one of the plurality of bit lines BL with reference to the column address.

The sense amplifier circuit33may include a plurality of bit line sense amplifiers connected to the memory cell array20through the plurality of bit lines BL. Among the plurality of bit line sense amplifiers, a bit line sense amplifier connected to a selected bit line among the plurality of bit lines BL selected by the column decoder34may read data of at least one selected memory cell among memory cells connected to the selected bit line, or may store data in the selected memory cell.

The selected memory cell may be a memory cell connected to a selected word line selected from among the plurality of word lines WL by the word line driving circuit31. As a degree of integration of the semiconductor device10gradually increases, a distance between the plurality of word lines WL may also tend to gradually decrease. Accordingly, while the word line driving circuit31drives the selected word line, adjacent unselected word lines may be affected. For example, as the word line driving circuit31changes a voltage level of the selected word line, parasitic capacitance existing between the selected word line and the unselected word line is charged and/or discharged, such that data of unselected memory cells connected to the unselected word line may be changed.

In example embodiments of the present disclosure, during at least a portion of a period in which the word line driving circuit31controls a voltage of the selected word line, at least one unselected word line, adjacent to the selected word line, among unselected word lines may be caused to float (i.e., may be floated). For example, the at least one unselected word line may be floated when it is not maintained at a reference voltage (described in further detail later with reference to, for example,FIGS.5to16). Accordingly, a voltage of the unselected word line may be reduced to a level lower than an initial level while the voltage of the selected word line decreases to the initial level, thereby reducing stress of the unselected word line, and preventing data loss of the unselected memory cells connected to the unselected word line.

FIG.2is a schematic diagram illustrating a structure of a semiconductor device according to example embodiments of the present disclosure.

Referring toFIG.2, each of a plurality of memory cells MC included in a memory cell array may include a cell capacitor CC and a cell switch SW. A control terminal of the cell switch SW may be connected to word lines WL0to WLn, and an input terminal of the cell switch SW may be connected to bit lines BL0to BLm or complementary bit lines BL0B to BLmB. For example, the control terminal of the cell switch SW may be a gate terminal and the input terminal of the cell switch SW may be a source/drain terminal, but the present disclosure is not limited thereto. The word lines WL0to WLn may be connected to sub-word line decoders SWD, and the bit lines BL0to BLm and the complementary bit lines BL0B to BLmB may be connected to bit line sense amplifiers BLSA. For example, the bit line sense amplifiers BLSA may be included in the sense amplifier circuit33ofFIG.1.

A control logic may decode a row address externally received to determine a selected word line from among the plurality of word lines WL0to WLn. The control logic may output a word line enable signal for activating the selected word line to the sub-word line decoders SWD. In addition, the control logic may decode the row address to generate driving signals for activating the selected word line, and may provide the driving signals to the sub-word line decoders SWD. For example, the control logic may be realized by using a hardware method, a software method, or a combination thereof.

The sub-word line decoders SWD may determine the selected word line in response to a word line enable signal and driving signals, and may increase a voltage level of the selected word line from an initial level to an active level. Accordingly, the cell switch SW included in each of the memory cells MC connected to the selected word line may be turned on. While a voltage of the selected word line is maintained at the active level, the bit line sense amplifier BLSA connected to a selected memory cell may read data from the selected memory cell through a selected bit line or write data to the selected memory cell.

When a control operation performed on the selected memory cell is completed, the voltage level of the selected word line may decrease back to the initial level from the active level. As described, while the voltage of the selected word line increases and decreases, data of unselected memory cells connected to an unselected word line disposed to be adjacent to the selected word line may be unintentionally changed.

In example embodiments of the present disclosure, in order to resolve the above-described issue, during a precharging period in which the voltage of the selected word line returns to the initial level, the unselected word line, adjacent to the selected word line, may be caused to float (i.e., may be floated) instead of being maintained at the initial level. For example, a time point at which the unselected word line floats may be before or after the voltage of the selected word line starts to decrease to the initial level. Accordingly, while the voltage of the selected word line decreases to the initial level, the voltage of the unselected word line may decrease to a level lower than the initial level, and data loss of unselected memory cells connected to the unselected word line may be prevented.

Each of the sub-word line decoders SWD may include a floating element not directly connected to one of the plurality of word lines WL0to WLn so as to cause at least one of the unselected word lines to float, as necessary. For example, the floating element may be connected between a switch element directly connected to one of the plurality of word lines WL0to WLn and a reference node supplying an initial level of voltage. For example, the reference node may supply a voltage at an initial level. In addition, the control logic may provide, to each of the sub-word line decoders SWD, a floating control signal for controlling whether each of the plurality of word lines WL0to WLn floats by turning on/off the floating element.

FIGS.3and4are schematic diagrams illustrating a structure of a portion of a memory cell array included in a semiconductor device according to example embodiments of the present disclosure. More specifically,FIG.3is a schematic plan view illustrating a structure of a portion of a memory cell array included in a semiconductor device according to example embodiments of the present disclosure, andFIG.4is a schematic cross-sectional view taken along line I-I′ ofFIG.3.

Referring toFIGS.3and4, a semiconductor memory device100according to example embodiments of the present disclosure may include a substrate101, and the substrate101may include an element isolation film102, and an active region103isolated by the element isolation film102. In addition, a plurality of gate structures110providing a plurality of word lines may be buried in or may extend in the substrate101. The plurality of bit lines may be provided by a plurality of bit line structures120extending in a direction, intersecting the plurality of gate structures110, and connected to at least a portion of the active region103.

Each of the plurality of gate structures110may include a gate insulating layer111, a gate electrode layer112, a capping layer113, and the like. The gate insulating layer111may be formed of silicon oxide, and the gate electrode layer112may be formed of a conductive material such as a metal, a metal compound, polysilicon, or the like. The capping layer113may be formed of an insulating material such as silicon nitride.

The active region103may be doped with impurities and may provide a source region and a drain region of a cell switch included in a memory cell. The portion of the active region103positioned between the gate structure110and the element isolation film102may be connected to a capacitor structure140through a first contact131. The portion of the active region103disposed between a pair of gate structures110adjacent to each other may be connected to one of the bit line structures120through a second contact132.

The plurality of bit line structures120along with the first contact131and the second contact132may be buried in or extend in one or more of intermediate insulating layers104and105. The intermediate insulating layers104and105may include a first intermediate insulating layer104and a second intermediate insulating layer105. Each of the plurality of bit line structures120may include a bit line conductive layer121, a bit line capping layer122, a spacer layer123, and the like.

The capacitor structure140may be connected to the active region103through the first contact131, and may include a lower electrode layer141, a dielectric layer142, an upper electrode layer143, and the like. The capacitor structure140may extend in a direction, perpendicular to an upper surface of the substrate101. As illustrated inFIG.4, the lower electrode layer141may have a column shape or a cylinder shape having an empty central portion.

Referring toFIG.4, as a left gate structure110is repeatedly selected (e.g., repeatedly activated by a selected word line) from among a pair of gate structures110adjacent to each other, an amount of charge of the capacitor structure140connected to a right gate structure110may be unintentionally changed. For example, when the left gate structure110is repeatedly selected such that a voltage thereof transitions between an active level and an initial level several times, accumulation and discharge of charges may be repeated in a channel region (e.g., a channel region of the active region103). In this case, charges of the capacitor structure140included in a memory cell provided by the right gate structure110may be lost, or data may be changed due to additional charges.

For example, when a voltage level of the right gate structure110is maintained at the initial level while the left gate structure110is repeatedly selected, some of the charges discharged from the channel region, adjacent to the left gate structure110, may flow into the capacitor structure140of a memory cell provided by the right gate structure110.

In example embodiments of the present disclosure, during at least a portion of a time period in which one of the plurality of gate structures110is selected, another gate structure110adjacent thereto may be caused to float (i.e., may be floated) to prevent the above-described issue. For example, the right gate structure110may be caused to float in at least a portion of a period in which a voltage of the left gate structure110decreases from the active level to the initial level. In this case, a voltage of the right gate structure110may decrease to a level lower than the initial level such that the voltage of the right gate structure110is under the influence (e.g., low enough to avoid or reduce the influence) of a decrease in a voltage level of the left gate structure110, thereby minimizing the flow of charges discharged from the channel region of the left gate structure110into the capacitor structure140of the memory cell provided by the right gate structure110. Accordingly, when a specific word line is repeatedly selected, a row hammer phenomenon in which data of unselected memory cells connected to another adjacent word line is affected may be effectively prevented.

FIG.5is a diagram illustrating an operation of a semiconductor device according to example embodiments of the present disclosure.

Referring toFIG.5, a semiconductor device according to example embodiments of the present disclosure may receive a row command signal CMD_ROW from an external host such as a central processing unit, an application processor, or the like. A control logic of the semiconductor device may determine selected word lines and unselected word lines from among a plurality of word lines with reference to the row command signal CMD_ROW and an address signal received together with the row command signal CMD_ROW.

The control logic may increase a voltage level of a selected word line in response to an activation command ACT (not shown) of the row command signal CMD_ROW. For example, the control logic may increase a voltage of the selected word line from an initial level Vinit to an active level Vpwr by controlling a sub-word line decoder connected to the selected word line in a word line driving circuit. Conversely, voltage levels of unselected word lines may be maintained as the initial level Vinit.

The control logic may perform a control operation for a selected memory cell connected to the selected word line using bit line sense amplifiers while the voltage of the selected word line is maintained at the active level Vpwr. For example, the control operation may include a program operation, a read operation, a refresh operation, and the like. When the control operation is terminated, a control logic circuit may control the sub-word line decoder connected to the selected word line to restore the voltage of the selected word line from the active level Vpwr to the initial level Vinit.

In example embodiments of the present disclosure, at least one unselected word line, adjacent to the selected word line, among unselected word lines may be caused to float (i.e., may be floated) while the voltage of the selected word line returns to the initial level Vinit. A voltage of the floating unselected word line may decrease to a level lower than the initial level Vinit as illustrated inFIG.5, in response to a decrease in the voltage of the adjacent selected word line. Accordingly, in a memory cell including a gate structure providing an unselected word line, a cell switch may be turned off, and charges flowing into a cell capacitor may be effectively blocked, thereby minimizing data loss of an unselected memory cell.

FIGS.6and7are schematic diagrams illustrating a sub-word line decoder included in a semiconductor device according to example embodiments of the present disclosure.

FIG.6is a circuit diagram illustrating a sub-word line decoder included in a memory device according to example embodiments of the present disclosure. Referring toFIG.6, the sub-word line decoder may include a plurality of switch elements PM1, NM1, and NM2and at least one floating element NM3. For example, the plurality of switch elements PM1, NM1, and NM2may be connected to each other in series, and may include a first switch element PM1being turned on and off by a word line control signal NWEIB, a second switch element NW, and a third switch element NM2. For example, the first switch element PM1may be connected in series with the second and third switch elements NM1and NM2, and the second and third switch elements NM1and NM2may be connected with each other in parallel. As illustrated inFIG.6, the second switch element NM1and the third switch element NM2may be connected to each other in parallel. For example, an element may be turned on (or similar language) when a current can flow freely therethrough. For example, an element may be turned off (or similar language) when little to no current can flow therethrough (e.g., a leakage current may still exist). When an element is turned off, it may still be considered to be electrically connected to another element or between other elements, but little to no current may flow through the element.

The first switch element PM1may be a PMOS transistor, and the second switch element NM1may be an NMOS transistor. In example embodiments, a first driving signal PXID may be input into the first switch element PM1, and the second switch element NM1may be connected to the floating element NM3. The first driving signal PXID may have different levels depending on whether a word line WL connected to the sub-word line decoder is a selected word line. For example, a node that has the first driving signal PXID may be a driving node, and a voltage at the driving node may be a voltage of the first driving signal PXID. For example, the driving node may supply the first driving signal PXID. The first switch element PM1may be connected between the driving node and a word line WL connected to the sub-word line decoder.

The third switch element NM2may be turned on and off by a second driving signal PXIB. In the same manner as the second switch element NW, the third switch element NM2may be connected to a reference node supplying a reference voltage VSS through the floating element NM3. For example, the reference node may supply a voltage at an initial level. In other words, a voltage at the reference node may be a reference voltage VSS. Accordingly, when the floating element NM3is turned on, the reference voltage VSS may be input into the second switch element NM1and the third switch element NM2.

The floating element NM3may be turned on and off by a floating control signal FLOATB. When the second switch element NM1and the third switch element NM2are turned on and the floating element NM3is also turned on, the reference voltage VSS corresponding to an initial level may be input into the word line WL. Conversely, when the second switch element NM1and the third switch element NM2are turned on and the floating element NM3is turned off, the word line WL may float.

As described above, a control logic of a semiconductor device may control the plurality of switch elements PM1, NW, and NM2and the floating element NM3to adjust a voltage level of the word line WL or to cause the word line WL to float. For example, when the word line WL is a selected word line, the control logic may turn on the first switch element PM1and turn off the second switch element NM1and the third switch element NM2. In addition, a voltage of the word line WL may be increased to an active level by increasing a level of the first driving signal PXID.

Conversely, when the word line WL is an unselected word line, the control logic may turn off the first switch element PM1and turn on the second switch element NM1and the third switch element NM2. In addition, the control logic may also turn on the floating element NM3to input the reference voltage VSS corresponding to the initial level into the word line WL.

When the word line WL is an unselected word line, not adjacent to the selected word line, the control logic may connect the word line WL to the reference node until a control operation performed on the selected memory cell is completed and a voltage of the selected word line returns to the initial level. Accordingly, the voltage of the word line WL may be continuously maintained as the reference voltage VSS. For example, the control logic may be configured to set respective voltages of unselected word lines, not adjacent to the selected word line, to the initial level.

When the word line WL is an unselected word line, adjacent to the selected word line, the control logic may turn on the second switch element NM1and the third switch element NM2and turn off the first switch element PM1and the floating element NM3in at least a portion of a period in which the voltage of the selected word line returns to the initial level. Accordingly, the word line WL may float. The floating word line WL may decrease to a voltage at a level lower than the reference voltage VSS such that the voltage of the floating word line WL is under the influence (e.g., low enough to avoid or reduce the influence) of a precharging operation in which the voltage of the adjacent selected word line returns to the initial level, thereby effectively preventing data loss of unselected memory cells connected to the word line WL.

FIG.7is a diagram illustrating a connection relationship between sub-word line decoders SWD1to SWD16and control signals. Referring toFIG.7, among the plurality of sub-word line decoders SWD1to SWD16included in a word line driving circuit200, some sub-word line decoders adjacent to each other may be grouped into decoder groups210and220. In the example embodiment illustrated inFIG.7, each of the decoder groups210and220may include eight of the plurality of sub-word line decoders SWD1to SWD16.

A first word line control signal NWEIB1may be input in common into first to eighth sub-word line decoders SWD1to SWD8of a first decoder group210, and a second word line control signal NWEIB2may be input in common into ninth to sixteenth sub-word line decoders SWD9to SWD16of a second decoder group220.

One of first to eighth driving signals PXIB1to PXIB8may be input in common into an i-th (i is a natural number from 1 to 8) sub-word line decoder of the first decoder group210and an i-th sub-word line decoder of the second decoder group220. For example, the ninth sub-word line decoder SWD9may be considered a first sub-word line decoder SWD9of the second decoder group220, the tenth sub-word line decoder SWD10may be considered a second sub-word line decoder SWD10of the second decoder group220, and the eleventh to sixteenth sub-word line decoders SWD11to SWD16may be considered in the same manner. As described above with reference toFIG.6, each of the first to eighth driving signals PXIB1to PXIB8may be a signal input into a first switch element included in each of the sub-word line decoders SWD1to SWD16.

When the plurality of sub-word line decoders SWD1to SWD16are implemented as illustrated inFIG.7in the word line driving circuit200, the control logic can control the plurality of sub-word line decoders SWD1to SWD16depending on whether a sub-word line decoder connected to an unselected word line, adjacent to the selected word line, and a sub-word line decoder connected to the selected word line are commonly included in one of the decoder groups210and220. Hereinafter, an operation according to a connection relationship between each of the selected word line and the unselected word line and the sub-word line decoders SWD1to SWD16will be described.

FIG.8is a schematic diagram illustrating a semiconductor device according to example embodiments of the present disclosure.FIG.9is a diagram illustrating an operation of a semiconductor device according to example embodiments of the present disclosure.

Referring toFIG.8, a semiconductor device300according to example embodiments may include a memory cell array310, sub-word line decoders320and330, and the like. The memory cell array310may include a plurality of memory cells MC. The memory cell array310may be connected to the sub-word line decoders320and330through a plurality of word lines WLn and WLn+1.

A structure of each of the sub-word line decoders320and330may be as described above with reference toFIG.6. Referring toFIG.8, each of the sub-word line decoders320and330may include first to third switch elements PM1, NM1, and NM2and a floating element NM3. In the example embodiment illustrated inFIG.8, a word line control signal NWEIB1may be input in common into an n-th sub-word line decoder320and an n+1-th sub-word line decoder330. Accordingly, as described above with reference toFIG.7, the n-th sub-word line decoder320and the n+1-th sub-word line decoder330may be included in the same decoder group. For example, n may be a positive natural number. First driving signals PXID1and PXID2and second driving signals PXIB1and PXIB2, input into the n-th sub-word line decoder320and the n+1-th sub-word line decoder330, may be different from floating control signals FLOATB1and FLOATB2.

An operation of the semiconductor device300according to the example embodiment illustrated inFIG.8will be described with reference toFIG.9. In the example embodiment illustrated inFIG.9, an n-th word line WLn may be determined as a selected word line, and an n+1-th word line WLn+1 may be determined as an unselected word line.

Referring toFIGS.8and9, when the word line control signal NWEIB1decreases from a high logic level H to a low logic level L, a first driving signal PXID1, input into the n-th sub-word line decoder320, may increase from the low logic level L to the high logic level H. In the n-th sub-word line decoder320, the first switch element PM1may be turned on and the second switch element NM1may be turned off, and the first driving signal PXID1may be input into the n-th word line WLn. Accordingly, a voltage of the n-th word line WLn may increase from the initial level Vinit to the active level Vpwr.

Conversely, a second driving signal PXIB1, input into the n-th sub-word line decoder320, may decrease from the high logic level H to the low logic level L, and the floating control signal FLOATB1may be maintained at the high logic level H. Accordingly, in the n-th sub-word line decoder320, the third switch element NM2may be turned off, and the floating element NM3may be maintained in an ON state.

Referring toFIGS.8and9, when the word line control signal NWEIB1decreases from the high logic level H to the low logic level L, a first driving signal PXID2, input into the n+1-th sub-word line decoder330, may be maintained at the low logic level L. In addition, a second driving signal PXIB2and a floating control signal FLOATB2, input into the n+1-th sub-word line decoder330, may be maintained at the high logic level H. Accordingly, the reference voltage VSS may be input into the n+1-th word line WLn+1, and a voltage of the n+1-th word line WLn+1 may be maintained at an initial level corresponding to the reference voltage VSS.

When a control operation performed on at least one selected memory cell among the memory cells MC connected to the n-th word line WLn is completed, the voltage of the n-th word line WLn may decrease from the active level Vpwr to the initial level Vinit. In the example embodiment illustrated inFIG.9, at a first time point t1, the word line control signal NWEIB1and the second driving signal PXIB1may transition to the high logic level H, and the first driving signal PXID1may transition to the low logic level L. Accordingly, at the first time point t1, the reference voltage VSS may be input into the n-th word line WLn by the n-th sub-word line decoder320, and the voltage of the n-th word line WLn may decrease from the active level Vpwr to the initial level Vinit.

Referring toFIGS.8and9, in the n+1-th sub-word line decoder330, the floating control signal FLOATB2may transition to the low logic level L at the first time point t1. For example, a logic level of the floating control signal FLOATB2may be set to the low logic level L during at least a portion of a precharging period in which a voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit. For example, a voltage of the low logic level L may correspond to a voltage at the initial level (e.g., a reference voltage VSS). In other words, a voltage of the floating control signal FLOATB2may be set to the initial level Vinit during at least a portion of a precharging period in which a voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit. Accordingly, the floating element NM3of the n+1-th sub-word line decoder330may be turned off, and the n+1-th word line WLn+1 may float. For example, a second time period ΔT2in which the n+1-th word line WLn+1 floats may be longer than a first time period ΔT1in which the voltage of the n-th word line WLn decreases to the initial level Vinit. For example, the first time period ΔT1may correspond to a precharging period in which a voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit.

As the floating element NM3is turned off at the first time point t1, the voltage of the n+1-th word line WLn+1 may decrease to a floating level Vft lower than the initial level Vinit. This may be because the voltage of the n-th word line WLn, adjacent to the n+1-th word line WLn+1, decreases from the active level Vpwr to the initial level Vinit. For example, the voltage of the n+1-th word line WLn+1 may be set to a floating level Vft that is lower than the initial level Vinit during at least a portion of a period in which the voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit. For example, a second voltage difference ΔV2between the initial level Vinit and the floating level Vft may be less than a first voltage difference ΔV1between the active level Vpwr and the initial level Vinit. For example, a voltage variation range (e.g., ΔV1) of the n-th word line WLn (e.g., the selected word line) may be greater than a voltage variation range (e.g., ΔV2) of the n+1-th word line WLn+1 (e.g., the unselected word line).

In example embodiments, the floating control signal FLOATB2, input into the n+1-th sub-word line decoder330, may transition back to the high logic level H after the second time period ΔT2elapses, such that the floating element NM3may be turned on, and the voltage of the n+1-th word line WLn+1 may increase to the initial level Vinit. During at least portion of the first time period ΔT1in which the voltage of the n-th word line WLn decreases, the voltage of the adjacent n+1-th word line WLn+1 may be reduced to the floating level Vft lower than the initial level Vinit, thereby preventing charges discharged from a channel region adjacent to a gate structure providing the n-th word line WLn from flowing into memory cells connected to the n+1-th word line WLn+1. Accordingly, loss and/or change of data of unselected memory cells connected to an unselected word line, adjacent to a selected word line, may be minimized.

FIG.10is a schematic diagram illustrating a semiconductor device according to example embodiments of the present disclosure.FIGS.11to13are diagrams illustrating an operation of a semiconductor device according to example embodiments of the present disclosure.

Referring toFIG.10, a semiconductor device400according to example embodiments of the present disclosure may include a memory cell array410, sub-word line decoders420and430, and the like. The memory cell array410may include a plurality of memory cells MC. The memory cell array410may be connected to the sub-word line decoders420and430through a plurality of word lines WLn and WLn+1.

Each of the sub-word line decoders420and430may include first to third switch elements PM1, NM1, and NM2, and a floating element NM3. In the example embodiment illustrated inFIG.10, a first word line control signal NWEIB1may be input into an n-th sub-word line decoder420, and a second word line control signal NWEIB2may be input into an n+1-th sub-word line decoder430. Accordingly, as described above with reference toFIG.7, the n-th sub-word line decoder420and the n+1-th sub-word line decoder430may be grouped into different decoder groups. First driving signals PXID1and PXID2and second driving signals PXIB1and PXIB2, input into the n-th sub-word line decoder420and the n+1-th sub-word line decoder430, may be different from floating control signals FLOATB1and FLOATB2.

An operation of the semiconductor device400according to the example embodiment illustrated inFIG.10will be described with reference toFIGS.11to13. In each of the example embodiments illustrated inFIGS.11to13, the n-th word line WLn may be determined as a selected word line, and the n+1-th word line WLn+1 may be determined as an unselected word line.

First, an operation according to the example embodiment illustrated inFIG.11may be similar to that described above with reference toFIG.9. The first driving signal PXID1, input into the n-th sub-word line decoder420, may transition to the high logic level H, and the second driving signal PXIB1and the word line control signal NWEIB1may transition to the low logic level L, such that a voltage of the n-th word line WLn may increase from the initial level Vinit to the active level Vpwr. Conversely, the first driving signal PXID2, input into the n+1-th sub-word line decoder430, may be maintained at the low logic level L, and the word line control signal NWEIB2and the second driving signal PXIB2may be maintained at the high logic level H. Accordingly, a voltage of the n+1-th word line WLn+1 may be maintained at the initial level Vinit.

The voltage of the n-th word line WLn may decrease from the active level Vpwr to the initial level Vinit during the first time period ΔT1starting from the first time point t1. Referring toFIGS.10and11, the floating control signal FLOATB2, input into the n+1-th sub-word line decoder430, may transition to the low logic level L at the first time point t1, such that the floating element NM3may be turned off, and the n+1-th word line WLn+1 may float from the first time point t1. For example, a voltage of the floating control signal FLOATB2may be set to the initial level Vinit during at least a portion of a precharging period in which a voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit. Accordingly, the voltage of the n+1-th word line WLn+1 may decrease to the floating level Vft lower than the initial level Vinit under the influence of a decrease in the voltage of the adjacent n-th word line WLn.

As described above, the floating control signal FLOATB2may turn off the floating element NM3during the second time period ΔT2. In addition, the second voltage difference ΔV2between the initial level Vinit and the floating level Vft may be less than the first voltage difference ΔV1between the initial level Vinit and the active level Vpwr.

In the example embodiment illustrated inFIG.12, the n+1-th word line WLn+1 may float at a second time point t2earlier than the first time point t1. In other words, while the voltage of the n-th word line WLn is maintained at the active level Vpwr, the n+1-th word line WLn+1 may float first. For example, the n+1-th word line WLn+1 may be floated during at least a portion of a period in which the voltage of the n-th word line WLn is maintained at the active level Vpwr. Referring toFIG.12, the second time period ΔT2in which the n+1-th word line WLn+1 is caused to float by the floating control signal FLOATB2may start earlier than the first time period ΔT1in which the voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit, and may end later than the first time period ΔT1.

In the example embodiment illustrated inFIG.13, the n+1-th word line WLn+1 may float at a third time point t3later than the first time point t1. The third time point t3may belong to the first time period ΔT1in which the voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit. In other words, while the voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit, the floating element NM3of the n+1-th sub-word line decoder430may be turned off. For example, the voltage of the n-th word line WLn may begin to decrease from the active level Vpwr to the initial level Vinit before the floating element NM3of the n+1-th sub-word line decoder430is turned off, but may not decrease entirely from the active level Vpwr to the initial level Vinit before the floating element NM3of the n+1-th sub-word line decoder430is turned off. For example, a logic level of the floating control signal FLOATB2may be set to the high logic level H during at least a portion of a precharging period in which a voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit. For example, a voltage of the high logic level H may correspond to a voltage that is higher than the initial level Vinit. In other words, a voltage of the floating control signal FLOATB2may be set to a voltage higher than the initial level Vinit during at least a portion of a precharging period in which a voltage of the n-th word line WLn decreases from the active level Vpwr to the initial level Vinit. Accordingly, as illustrated inFIG.13, a portion of the first time period ΔT1may overlap the second time period ΔT2.

FIGS.14to16are diagrams illustrating an operation of a semiconductor device according to example embodiments of the present disclosure.

In example embodiments described with reference toFIGS.14to16, a control logic of a semiconductor device500may select the n-th word line WLn as a selected word line, and select the n+1-th word line WLn+1 as an unselected word line in a memory cell array510. Referring first toFIG.14, in an n-th sub-word line decoder520connected to the selected word line, the first switch element PM1may be turned on, and the second switch element NM1and the third switch element NM2may be turned off.

The floating element NM3can be turned on by the floating control signal FLOATB1. However, since the second switch element NM1and the third switch element NM2are turned off, a voltage of the n-th word line WLn may be determined depending on the first driving signal PXID1rather than the reference voltage VSS. The control logic of the semiconductor device500may increase a level of the first driving signal PXID1, thereby increasing the voltage of the n-th word line WLn to an active level, and turning on the cell switch SW of each of the memory cells MC connected to the n-th word line WLn.

In an n+1-th sub-word line decoder530connected to the unselected word line, the first switch element PM1may be turned off, the second switch element NM1, the third switch element NM2, and the floating element NM3may be turned on. Accordingly, the reference voltage VSS may be input into the n+1-th word line WLn+1 by the n+1-th sub-word line decoder530, and the cell switch SW of each of the memory cells MC connected to the n+1-th word line WLn+1 may be maintained in an OFF state.

The control logic of the semiconductor device500may perform a control operation on at least one of the memory cells MC connected to the n-th word line WLn using bit line sense amplifiers. When the control operation is completed, the control logic may decrease the voltage of the n-th word line WLn. Referring toFIG.15, in the n-th sub-word line decoder520, the first switch element PM1may be turned off, and the second switch element NM1and the third switch element NM2may be turned on. Accordingly, the reference voltage VSS may be input into the n-th word line WLn, and the voltage of the n-th word line WLn may be initialized to an initial level.

The control logic may cause the n+1-th word line WLn+1, an unselected word line adjacent to the n-th word line WLn, to float while the voltage of the n-th word line WLn decreases to the initial level. Referring toFIG.15, in the n+1-th sub-word line decoder530, the floating element NM3may be turned off by the floating control signal FLOATB2, and accordingly neither the reference voltage VSS nor the first driving signal PXID2may be input into the n+1-th word line WLn+1.

In a floating state, a voltage of the n+1-th word line WLn+1 may decrease to a level lower than the initial level under the influence of a decrease in the voltage of the adjacent n-th word line WLn. Accordingly, the cell switch SW of each of the memory cells MC connected to the n+1-th word line WLn+1 may be turned off more strongly than the state described with reference toFIG.14, the cell switches SW connected to the n-th word line WLn may be turned off, and charges discharged from a channel region may not flow into the cell capacitors CC of the memory cells MC connected to the n+1-th word line WLn+1, thereby preventing change and/or loss of data of the memory cells MC connected to the unselected word line, and improving reliability of the semiconductor device500.

Subsequently, referring toFIG.16, in the n+1-th sub-word line decoder530, the floating element NM3may be turned on by the floating control signal FLOATB2after a predetermined time period elapses. Accordingly, the n+1-th word line WLn+1 may be connected to the reference node, and the voltage of the n+1-th word line WLn+1 may return to the initial level.

In some example embodiments of the present disclosure, during at least a portion of a precharging period in which a voltage of a selected word line returns from an active level to an initial level, an unselected word line, adjacent to the selected word line, may not completely float. For example, in a sub-word line decoder connected to the unselected word line, a floating element may not be completely turned off. A voltage between a turn-on voltage and a turn-off voltage may be input into the floating element, and thus the floating element may operate as a type of resistance element.

The floating element may be connected between a reference node supplying a reference voltage and some of a plurality of switch elements. Accordingly, while the floating element operates as a resistive element, it can be seen that an equivalent circuit in which the unselected word line is connected to the reference node through the resistance element is formed, and charges of the unselected word line may be removed through the floating element. Hereinafter, such a configuration will be described in more detail with reference toFIGS.17and18.

FIGS.17and18are diagrams illustrating an operation of a semiconductor device according to example embodiments of the present disclosure.

In example embodiments described with reference toFIGS.17and18, an intermediate voltage Vmid between a turn-on voltage and a turn-off voltage may be input into the floating element NM3of a sub-word line decoder600to which the word line WL is connected. When another word line, adjacent to the word line WL, is selected, the intermediate voltage Vmid may be input into the floating element NM3during at least a portion of a precharging period in which a voltage of the other word line returns from an active level to an initial level.

Referring toFIGS.17and18, in a period overlapping at least a portion of the precharging period in which the voltage of the selected word line decreases to the initial level, the intermediate voltage Vmid may be input into the floating element NM3of the sub-word line decoder600. The floating element NM3may be an NMOS transistor. The intermediate voltage Vmid may have a level higher than the low logic level L corresponding to a turn-off voltage of the floating element NM3, and lower than the high logic level H corresponding to a turn-on voltage of the floating element NM3.

As illustrated inFIG.18, the floating element NM3may operate as a type of resistance element. By the word line control signal NWEIB, the first switch element PM1may be turned off and the second switch element NM1may be turned on. The third switch element NM2may be turned on by the second driving signal PXIB. Accordingly, the word line WL may be connected to the floating element NM3operating as a resistance element.

Accordingly, the word line WL may be connected to a reference node supplying the reference voltage VSS through the sub-word line decoder600(e.g., through the floating element NM3), and a charge leakage path through which the leakage current ILEAKflows may be formed between the word line WL and the reference node. While a voltage of another word line, adjacent to the word line WL, decreases from the active level to the initial level, charges may be discharged from a channel region of cell switches connected to the another word line, and a parasitic capacitance component between the word line WL and the another adjacent word line may be charged due to the discharged charges.

In example embodiments of the present disclosure, if necessary, as illustrated inFIGS.17and18, a path through which the leakage current ILEAKflows may be generated by weakly turning on the floating element NM3. Accordingly, when parasitic capacitance between word lines is charged due to charges discharged during a turn-off operation of cell switches connected to a selected word line, the parasitic capacitance may be removed using the leakage current LEAK. For example, when a specific word line is repeatedly selected as the selected word line and accesses to the word line are accumulated, a control logic of a semiconductor device may control the sub-word line decoder600connected to another adjacent word line, as described with reference toFIGS.17and18, thereby removing the parasitic capacitance between the word lines.

As used herein, the terms “comprises”, “comprising”, “includes”, “including”, “has”, “having” and any other variations thereof specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

While example embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present disclosure as defined by the appended claims.