Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC 119 from Japanese Patent Application No. 2010-039209, filed on Feb. 24, 2010, the disclosure of which is incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the invention 
         [0003]    The present invention relates to a decoder circuit of a semiconductor storage device. In particular, the present invention relates to a decoder circuit of an electrically rewritable non-volatile semiconductor storage device. 
         [0004]    2. Description of the Related Art 
         [0005]    In a conventional non-volatile semiconductor storage device, such as a flash memory, a high-voltage transistor is incorporated therein, since the conventional non-volatile semiconductor storage device has to be applied with a high voltage when performing writing or erasing of data. However, it is necessary to increase the thickness of a gate oxide film and the length of a gate of the transistor to withstand a high voltage, which may deteriorate a driving force of the transistor. 
         [0006]    Japanese Patent Application Laid-Open (JP-A) No. 11-185489 discloses an X-decoder circuit that selects a word line by switching between a high-voltage driver circuit and a low-voltage driver circuit. This X-decoder circuit uses the high-voltage driver circuit when a high voltage is necessary, such as when writing or erasing data, and uses the low-voltage driver circuit when a high voltage is not necessary, such as when reading data. Due thereto, this X-decoder circuit prevents an operation speed from being lowered when a high voltage is not necessary. 
         [0007]    However, this X-decoder circuit has to include not only the high-voltage driver circuit but also the low-voltage driver circuit, which may increases the circuit area of the X-decoder circuit. 
         [0008]    JP-A No. 2007-310936 discloses a row decoder including a driver circuit in which a high-voltage transistor is used. 
         [0009]    However, this row decoder also uses the high-voltage transistor. Therefore, this row decoder may not perform an operation at high speed and the circuit area of the driver circuit may increase. 
         [0010]      FIG. 13  is a diagram illustrating an example of a conventional row decoder  100 . A row decoder  100  shown in  FIG. 13  selects a word line with reference to the address of a memory cell to be accessed, when accessing to the memory cell. The row decoder  100  applies a normal voltage to the selected word line when reading data, and applies a high voltage to the selected word line when writing or erasing data. 
         [0011]    As shown in  FIG. 13 , the row decoder  100  includes a level shift circuit  102  and a word line selection circuit  104 . The level shift circuit  102  includes high-voltage PMOS transistors P 101  and P 102 , NMOS transistors N 101  to N 104 , and an inverter  106 . The word line selection circuit  104  includes a high-voltage PMOS transistor P 103 , high-voltage PMOS transistors P 200  to P 20 n disposed for each signal HVXPB [n:0] respectively, and NMOS transistors N 300  to N 30 n, N 400  to N 40 n, and N 500  to N 50 n disposed for each signal XPB [n:0] respectively. 
         [0012]      FIG. 14  is a chart illustrating the voltage values of the respective signals in a normal operation (NORMAL) that uses a normal voltage when reading data, and in a high voltage operation (HV) that uses a high voltage when writing or erasing data, in selection and non-selection of the word lines.  FIG. 15A  is a diagram illustrating a timing chart of the respective signals in the normal operation.  FIG. 15B  is a diagram illustrating a timing chart of the respective signals in the high voltage operation. 
         [0013]    VPP shown in  FIG. 14  is a high voltage supplied from an external power supply (not shown). An example of VPP is 10.0 [V]. VCC is a voltage supplied from the external power supply (not shown). Examples of VCC are 3.0 to 4.0 [V]. VCW is a voltage supplied from an internal power supply (not shown) and an example of VCW is 3.6 [V]. VNN is a ground potential and an example of VNN is 0.0 [V]. 
         [0014]    SLCT is a signal that becomes “H” (high level: VCC) when any one of the word lines WL [n:0] is selected, irrespective to the normal operation or the high voltage operation,. The signal SLCT becomes “L” (low level: 0 V) when none of the word lines is selected, irrespective to the normal operation or the high voltage operation. 
         [0015]    When the signal SLCT becomes “H”, HVXPB [n:0] corresponding to the selected word line number becomes 0.0 [V] irrespective to the normal operation and the high voltage operation. Accordingly, in the normal operation, 3.6 [V] is supplied to the corresponding word line WL. Thus, in the high voltage operation, 10.0 [V] is supplied to the corresponding word line WL. 
         [0016]    HV_SLCTB is a signal that becomes “H” (VCW in the normal operation and VPP in the high voltage operation) in the non-selection of the word line. 
         [0017]    XPB is a signal that becomes “L” when a word line is selected, and becomes “H” when the word line is not selected, irrespective to the normal operation or the high voltage operation. 
         [0018]    VWLX is a signal that becomes VCW in the normal operation, and becomes VPP in the high voltage operation, irrespective to the selection or the non-selection of a word line. 
         [0019]    Hereinafter, an operation for selecting the word line WL 0  and supplying VCW to the word line WL 0  will be described as an example for the selecting a word line in the normal operation. 
         [0020]    In this case, SLCT=“H”, HVXPB [ 0 ]=0.0 [V], XPB [ 0 ]=“L”, HVXPB [n:1]=VCW=3.6 [V], and XPB [n:1]=“H” are input. Here, n is a positive integer, and HVXPB [n:0] and XPB [n:0] correspond to n+1 lines of word lines WLn to WL 0 . 
         [0021]    In this case, the level shift circuit  102  shifts the input SLCT=“H”=VCC to HV_SLCTB=“L”=0.0 [V], and outputs the shifted signal to the word line selection circuit  104 . 
         [0022]    The inverse signal of SLCT=“H” is input to the gates of the NMOS transistors N 500  to N 50 n of the word line selection circuit  104  by the inverter  106 . Accordingly, all the NMOS transistors N 500  to N 50 n become a non-conductive state. 
         [0023]    When the word line WL 0  is selected, HV_SLCTB is “L” and HVXPB [ 0 ] is “L”, and the-high-voltage PMOS transistors P 103  and P 200  are in a conductive state. Further, the NMOS transistor N 300  are in a non-conductive state based on XPB [ 0 ]=“L”. Accordingly, the word line WL 0  is connected to VWLX=VCW=3.6 [V] and is disconnected from VNN=0.0 [V], and, therefore, WL 0  becomes VCW=3.6 [V]. Since the other word lines WL are disconnected from the signal VWLX based on HVXPB [n:1]=VCW=3.6 [V] and XPB [n:1]=“H” and are connected to the signal VNN, WL [n:1] become 0.0 [V]. 
         [0024]    When SLCT=“H”, HVXPB [n:0]=0.0[V], and XPB [n:0]=“L”, all the word lines WL [n:0] may be selected, as in the above-described case of the selection of the word line WL 0 . Accordingly, WL [n:0] become VCW=3.6 [V]. 
         [0025]    Next, an operation when none of the word lines WL [n:0] is selected, will be described. In this case, SLCT=“L” is input. For HVXPB [n:0], input of VCW=3.6 [V] or VCW=0.0 [V] is allowed, and for XPB [n:0] an arbitrary input value of “H” or “L” is allowed. 
         [0026]    When SLCT is “L”, HV_SLCTB become “H”=3.6 [V]. Due thereto, the high-voltage PMOS transistor P 103  becomes a non-conductive state. On the other hand, all the NMOS transistors N 500  to N 50 n, into which the inverse signal of the signal SLCT is input, become a conductive state. Thus, since the word lines WL [n:0] are disconnected from the signal VWLX, and are connected to the signal VNN, WL [n:0] become 0.0 [V]. 
         [0027]    Next, an operation for selecting the word line WL 0  and supplying VPP=10.0 [V] to WL 0  will be described, as an example for the selecting a word line in the high voltage operation. In this case, SLCT=“H”, HVXPB [ 0 ]=0.0 [V], XPB [ 0 ]=“L”, HVXPB [n:1]=VPP=10.0 [V], and XPB [n:1]=“H” are input. 
         [0028]    The level shift circuit  102  shifts SLCT=“H”=VCC to HV_SLCTB=“L”=0.0 [V] and outputs the shifted signal to the word line selection circuit  104 , as in the normal operation. 
         [0029]    The inverse signal of SLCT=“H”, inverted by the inverter  106 , is input to the gates of the NMOS transistors N 500  to N 50 n of the word line selection circuit  104 . Therefore, all the NMOS transistors N 500  to N 50 n become a non-conductive state. 
         [0030]    When the word line WL 0  is selected, HVXPB [ 0 ] is “L”, XPB [ 0 ] is “L”, HVXPB [n:1] are VPP=10.0 [V], and XPB [n:1] are “H”. Thus, the high-voltage PMOS transistors P 103  and P 200  become a conductive state based on HV_SLCTB=0.0 [V] and HVXPB [ 0 ]=0.0 [V]. The NMOS transistor N 300  becomes a non-conductive state based on XPB [ 0 ]=“L”. Due thereto, the word line WL 0  is connected to VWLX=VPP=10.0 [V] and is disconnected from VNN=0.0 [V]. Accordingly, WL 0  becomes VPP=10.0 [V]. Since the other word lines WL are disconnected from the signal VWLX based on HVXPB [n:1]=VPP=10.0 [V] and XPB [n:1]=“H” and are connected to the signal VNN, WL [n:1] become 0.0 [V]. 
         [0031]    Note that when SLCT=“H”, HVXPB [n:0]=0.0 [V], and XPB [n:0]=“L”, all the word lines WL [n:0] may be selected, as in the above-described case of the selection of the word line WL 0 . Accordingly, WL [n:0] become VPP=10.0 [V]. 
         [0032]    Next, an operation for selecting none of the word lines WL [n:0] will be described. In this case, SLCT=“L” is input. For HVXPB [n:0], VPP=10.0 [V] or VPP=0.0 [V] may be input, and for XPB [n:0] an arbitrary input value of “H” or “L” may be input . 
         [0033]    By inputting SLCT=“L”, HV_SLCTB becomes “H”=10.0 [V]. Therefore, the high-voltage PMOS transistor P 103  becomes a non-conductive state. On the other hand, all the NMOS transistors N 500  to N 50 n, into which the inverse signal of the signal SLCT is input, become a conductive state. Thus, since the word lines WL [n:0] are disconnected from the signal VWLX, and is connected to the signal VNN, WL [n:0] become 0.0 [V].  FIG. 16  is a diagram illustrating the voltage state of the selection of a word line in the high voltage operation. Further,  FIG. 17  is a diagram illustrating the voltage state of the non-selection of a word line in the high voltage operation. 
         [0034]    As shown in  FIG. 16  and  FIG. 17 , in the conventional row decoder  100 , the high voltage in the range from 0.0 [V] to 10.0 [V] is applied to the electrodes of the PMOS transistors P 101  and P 102  of the level shift circuit  102 , and the PMOS transistors P 103 , P 200 , P 201 , . . . , P 20 n of the word line selection circuit  104 . Therefore, in the conventional row decoder  100 , these transistors have to resist the high voltage. Accordingly, the conventional row decoder  100  may not perform an operation at high speed and the circuit area of the driver circuit may increase. 
       SUMMARY OF THE INVENTION 
       [0035]    The present invention provides a decoder circuit of a semiconductor storage device that may prevent an increase in the area of a circuit and that may maintain a high operation speed. 
         [0036]    A first aspect of the present invention is a decoder circuit of a semiconductor storage device, including: a word line selection circuit that includes voltage application MOS transistors corresponding to each of a plurality of word lines that apply a normal voltage to the word lines corresponding to memory cells selected among a plurality of memory cells positioned at a portion where the plurality of word lines intersect a plurality of bit lines in a predetermined normal operation, and that applies a high voltage higher than the normal voltage in a predetermined high voltage operation; and a level shift circuit that outputs, to the voltage application MOS transistor, at least one of the normal voltage or a ground voltage lower than the normal voltage according to a selection state of the word line in the normal operation, and that outputs, to the voltage application MOS transistor, at least one of the normal voltage or the high voltage according to a selection state of the word line in the high voltage operation. 
         [0037]    A second aspect of the present invention, in the first aspect, the voltage application MOS transistors of the word line selection circuit may include PMOS transistors, the word line selection circuit may include a control PMOS transistor that controls output of a voltage to the voltage application MOS transistor, including a source to which the normal voltage is input when the word line selection circuit performs the normal operation, and to which the high voltage is input when the word line selection circuit performs the high voltage operation, and a drain connected to a source of the voltage application MOS transistor, and the level shift circuit may include, a PMOS transistor including a source to which the normal voltage is input in the normal operation, and to which the high voltage is input in the high voltage operation, and a gate to which the normal voltage is input when the word line is selected in the normal operation, to which the ground voltage is input when the word line is not selected in the normal operation, and to which the normal voltage is constantly input in the high voltage operation, a first DMOS transistor, connected to the PMOS transistor in series, including a gate and a source connected to a gate of the control PMOS transistor, a second DMOS transistor, connected to the first DMOS transistor in series, including a gate to which a selection signal, that becomes active when the word line is selected, is input, a first NMOS transistor, connected to the second DMOS transistor in series, including a gate to which the selection signal is input, and a second NMOS transistor, connected to the first NMOS transistor in parallel, including a gate to which the ground voltage is input in the normal operation, and to which the high voltage is input in the high voltage operation, and a source to which the ground voltage is input in the normal operation, and to which the normal voltage is input in the high voltage operation. 
         [0038]    A third aspect of the present invention, in the first aspect, the voltage application MOS transistors of the word line selection circuit may include PMOS transistors including a source to which the normal voltage is input in the normal operation and to which the high voltage is input in the high voltage operation, and the level shift circuit may include, a PMOS transistor including a source to which the normal voltage is input in the normal operation, and to which the high voltage is input in the high voltage operation, and a gate to which the normal voltage is input when the word line is selected in the normal operation, to which the ground voltage is input when the word line is not selected in the normal operation, and to which the normal voltage is constantly input in the high voltage operation, a first DMOS transistor, connected to the PMOS transistor in series, including a gate and a source connected to a gate of the voltage application MOS transistor, a second DMOS transistor, connected to the first DMOS transistor in series, including a gate to which a selection signal, that becomes active when the word line is selected, is input, a first NMOS transistor, connected to the second DMOS transistor in series, including a gate to which the selection signal is input, and a second NMOS transistor, connected to the first NMOS transistor in parallel, including a gate to which the ground voltage is input in the normal operation, and to which the high voltage is input in the high voltage operation, and a source to which the ground voltage is input in the normal operation, and to which the normal voltage is input in the high voltage operation. 
         [0039]    A fourth aspect of the present invention, in the above aspect, may further include a third DMOS transistor connected to the first DMOS transistor in parallel. 
         [0040]    According to the present invention, an increase in the area of a circuit may be prevented, and a high operation speed may be maintained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]    Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
           [0042]      FIG. 1  is a schematic diagram illustrating a configuration of a semiconductor storage device according to a first exemplary embodiment; 
           [0043]      FIG. 2  is a circuit diagram illustrating a row decoder according to the first exemplary embodiment; 
           [0044]      FIG. 3  is a chart illustrating signals of the portions of the row decoder according to the first exemplary embodiment; 
           [0045]      FIG. 4A  is a diagram illustrating the voltages at the portions of the row decoder in normal operation, according to the first exemplary embodiment; 
           [0046]      FIG. 4B  is a diagram illustrating the voltages at the portions of the row decoder in high voltage operation, according to the first exemplary embodiment; 
           [0047]      FIG. 5  is a circuit diagram illustrating a row decoder according to a second exemplary embodiment; 
           [0048]      FIG. 6  is a chart illustrating signals of the portions of the row decoder according to the second exemplary embodiment; 
           [0049]      FIG. 7A  is a diagram illustrating the voltages at the portions of the row decoder in normal operation, according to the second exemplary embodiment; 
           [0050]      FIG. 7B  is a diagram illustrating the voltages at the portions of the row decoder in high voltage operation according to the second exemplary embodiment; 
           [0051]      FIG. 8  is a diagram illustrating the voltage at the portions of the row decoder when a word line is selected in the high voltage operation, according to the second exemplary embodiment; 
           [0052]      FIG. 9  is a diagram illustrating the voltage at the portions of the row decoder when no word line is selected in the high voltage operation, according to the second exemplary embodiment; 
           [0053]      FIG. 10  is a circuit diagram illustrating a row decoder according to a third exemplary embodiment; 
           [0054]      FIG. 11  is a chart illustrating signals of the portions of the row decoder according to the third exemplary embodiment; 
           [0055]      FIG. 12  is a circuit diagram illustrating a row decoder according to a fourth exemplary embodiment; 
           [0056]      FIG. 13  is a circuit diagram illustrating a conventional row decoder; 
           [0057]      FIG. 14  is a chart illustrating signals of the portions of the conventional row decoder; 
           [0058]      FIG. 15A  is a diagram illustrating the voltages at the portions of the conventional row decoder in normal operation; 
           [0059]      FIG. 15B  is a diagram illustrating the voltages at the portions of the conventional row decoder in high voltage operation; 
           [0060]      FIG. 16  is a diagram illustrating the voltage at the portions of the conventional row decoder when a word line is selected in the high voltage operation; and 
           [0061]      FIG. 17  is a diagram illustrating the voltage at the portions of the conventional row decoder when no word line is selected in the high voltage operation. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0062]    Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. 
       First Exemplary Embodiment   
       [0063]    Hereinafter, a first exemplary embodiment of the present invention will be described. The same reference numerals are given to the same portions as those of  FIG. 13  and  FIG. 14  described above, and the detailed description thereof will be omitted. 
         [0064]      FIG. 1  is a schematic diagram illustrating a configuration of a semiconductor storage device  10 . As shown in  FIG. 1 , the semiconductor storage device  10  includes a memory cell array  12  in which plural memory cells including a MOS transistor or the like are arranged. Namely, in the memory cell array  12 , plural word lines WL disposed in a column direction are arranged to intersect plural bit lines BL disposed in a row direction perpendicular to the column direction. In the memory cell array  12 , memory cells (not shown) are disposed at the intersecting portion of the word lines WL and the bit lines BL, respectively. 
         [0065]    A gate of each memory cell is connected to the word line WL. A source and a drain of each memory cell are connected to the bit line BL. 
         [0066]    The word lines WL are connected to a row decoder  14 , and the bit lines BL are connected to a column decoder  16 . The row decoder  14  and the column decoder  16  are connected to a controller  18 . 
         [0067]    The controller  18  controls an operation such as writing, reading, or erasing of data to/or/from the memory cell array  12 . When receiving operation for any one of writing, reading, and erasing of data from the outside, the controller  18  outputs voltages or signals to the row decoder  14  or the column decoder  16 , to select the word lines WL or the bit lines BL depending on the details of the received operation. 
         [0068]      FIG. 2  is a circuit diagram illustrating the row decoder  14 . according to this exemplary embodiment. As shown in  FIG. 2 , the row decoder  14  includes an LV_SLCT signal output circuit  20 , a level shift circuit  22 , and a word line selection circuit  24 . 
         [0069]    The LV_SLCT output circuit  20  includes an inverter  26  and an NAND circuit  28 . A signal HVXB from the controller  18  is input to one input terminal of the NAND circuit  28 . An output signal of the inverter  26  is input to the other input terminal of the NAND circuit  28 . The NAND circuit  28  outputs a signal LV_SLCT, which is a negative logic signal of the inputted signals, to the level shift circuit  22 . 
         [0070]    The level shift circuit  22  includes a PMOS transistor P 1 , DMOS transistors D 1  and D 2 , and NMOS transistors N 1  and N 2 . 
         [0071]    Signals LV_SLCT, SLCT, VWLX, HVXD, and VWLXD are input from the controller  18  to the level shift circuit  22 , and a signal HV_SLCTB is output to the word line selection circuit  24 , depending on the input status of the above signals. 
         [0072]    The word line selection circuit  24  includes a PMOS transistor P 2 ; PMOS transistors P 30 , P 31 , . . . , P 3 n disposed for each HVXPB [n:0] signals; PMOS transistors P 30 A, P 31 A, . . . , P 3 nA to which a signal VWLXP is input and which are disposed in accordance with the number lines of word lines WL; and NMOS transistors N 30 , N 31 , . . . , N 3 n, N 40 , N 41 , . . . , N 4 n, and N 50 , N 51 , . . . , N 5 n disposed for each XPB [n:0] signals. 
         [0073]      FIG. 3  is a chart illustrating the voltage values of the signals in normal operation (NORMAL) that uses a normal voltage when reading data, and in high voltage operation (HV) that uses a high voltage, for example, when writing or erasing data, in selection and non-selection of the word lines.  FIG. 4A  is a diagram illustrating a timing chart of the respective signals in the normal operation.  FIG. 4B  is a diagram illustrating a timing chart of the respective signals in the high voltage operation. 
         [0074]    VPP shown in  FIG. 3  is a high voltage supplied from an external power supply (not shown). An example of VPP is 10.0 [V]. VCC is a voltage supplied from the external power supply (not shown). Examples of VCC are 3.0 to 4.0 [V]. VNN is a ground potential and an example of VNN is 0.0 [V]. 
         [0075]    Irrespective to the normal operation or the high voltage operation, SLCT becomes “H” when any one of the word lines WL [n:0] is selected. Further, irrespective to the normal operation or the high voltage operation, the SLCT becomes “L” when none of the word lines are selected. Here, “H” is VCC=3.0 [V] and “L” is 0.0 [V]. 
         [0076]    When the SLCT becomes “H”, HVXPB [n:0] corresponding to the selected word line becomes 3.0 [V] in the normal operation, and becomes 10.0 [V] in the high voltage operation. Accordingly, in the normal operation, 3.0 [V] is supplied to the selected word line WL, and in the high voltage operation, 10.0 [V] is supplied to the selected word line WL. 
         [0077]    HVXB becomes “H” in the normal operation and becomes “L” in the high voltage operation, irrespective to the selection or the non-selection of a word line. 
         [0078]    VWLX becomes 3.0 [V] in the normal operation and becomes 10.0 [V] in the high voltage operation, irrespective to the selection or the non-selection of a word line. 
         [0079]    HVXD becomes 0.0 [V] in the normal operation and becomes 10.0 [V] in the high voltage operation, irrespective to the selection or the non-selection of a word line. 
         [0080]    VWLXD becomes 0.0 [V] in the normal operation and becomes 3.0 [V] in the high voltage operation, irrespective to the selection or the non-selection of a word line. 
         [0081]    XPB becomes “L” in the selection of a word line and becomes “H” in the non-selection of a word line, irrespective to the normal operation or the high voltage operation. 
         [0082]    VNN is 0.0 [V] irrespective to the selection of a word line, the non-selection of a word line, the normal operation, and the high voltage operation. 
         [0083]    First, an operation for selecting a word line in the normal operation will be described. 
         [0084]    When selecting a word line WL, the controller  18  outputs the signal HVXB=“H” to the LV_SLCT output circuit  20 . 
         [0085]    Further, the controller  18  outputs HVXD=0.0 [V], VWLXD=0.0 [V], and the VWLX=VCC=3.0 [V] to the level shift circuit  22 . 
         [0086]    Furthermore, the controller  18  outputs VWLXP=0.0 [V] and VNN=0.0 [V] to the word line selection circuit  24 . 
         [0087]    Hereinafter, an operation for selecting the word line WL 0  and supplying the signal VCC to the word line WL 0 , will be described as an example for selecting a word line in the normal operation. Note that, “H”=VCC=3.0 [V] and “L”=0.0 [V]. 
         [0088]    In this case, the controller  18  outputs SLCT=“H”, HVXPB [ 0 ]=0.0 [V], XPB [ 0 ]=“L”, HVXPB [n:1]=VCC=3.0 [V], and XPB [n:1]=“H” to each circuit. Note that, n is a positive integer, and HVXPB [n:0] and XPB [n:0] correspond to n+1 lines of the word lines WL. 
         [0089]    An operation of the LV_SLCT output circuit  20  will be described. The LV_SLCT output circuit  20  operates as LV_SLCT=SLCT based on HVXB=“H”. Accordingly, LV_SLCT becomes “H” because of SLCT=“H”. 
         [0090]    Next, an operation of the level shift circuit  22  will be described. DMOS transistors D 1  and D 2  are in a conductive state based on HVXD=0.0 [V], VWLXD=0.0 [V], and VWLX=VCC=3.0 [V], irrespective to the logical value of SLCT and LV_SLCT. Therefore, the level shift circuit  22  operates as an inverter circuit configured by the PMOS transistor P 1  and the NMOS transistor N 1 . Accordingly, the level shift circuit  22  outputs the LV_SLCT=“H” input from the LV_SLCT output circuit  20 , as HV_SLCTB=“L” to the word line selection circuit  24 . 
         [0091]    Hereinafter, an operation of the word line selection circuit  24  will be described. All the NMOS transistors N 50 , N 51 , . . . , N 5 n in which the inverse logic of SLCT is input to the gates become a non-conductive state based on SLCT=“H”. Here, to select the word line WL 0 , HVXPB [ 0 ] is 0.0 [V], XPB [ 0 ] is “L”, HVXPB [n:1] are VCC=3.0 [V], and XPB [n:1] are “H”. The PMOS transistors P 2 , P 30 , and P 30 A become a conductive state based on HV_SLCTB=“L”, HVXPB [ 0 ]=0.0 [V], and VWLXP=0.0 [V]. The NMOS transistor N 30  becomes a non-conductive state based on XPB [ 0 ]=“L”. Due thereto, the word line WL 0  is connected to VWLX=VCC=3.0 [V] and is disconnected from VNN=0.0 [V]. Accordingly, word line WL 0  becomes VCC=3.0 [V]. Further, the other word lines WL are disconnected from VWLX and are connected to VNN based on HVXPB [n:1]=3.0 [V] and XPB [n:1]=“H”. Accordingly, WL [n:1] become 0.0 [V]. 
         [0092]    Note that when SLCT=“H”, HVXPB [n:0]= 0 . 0  [V], and XPB [n:0]=“L”, all the word lines WL [n:0] may be selected, as in the above-described case of the selection of the word line WL 0 . Accordingly, WL [n:0] become VCC=3.0 [V]. 
         [0093]    Next, an operation for selecting none of the word lines WL [n:0] will be described. In this case, the controller  18  outputs SLCT=“L” to the LV_SLCT output circuit  20 . For HVXPB [n:0], an in put of VCC=3.0 [V] may be input, and for XPB [n:0] an arbitrary input value of “H” or “L” may be input. 
         [0094]    By inputting SLCT=“L”, LV_SLCT=0.0 [V] becomes HV_SLCTB=3.0 [V]. Therefore, the PMOS transistor P 2  becomes a non-conductive state. On the other hand, all the NMOS transistors N 50 , N 51 , . . . , N 5 n, into which the inverse logic of the signal SLCT is input, become a conductive state. Due thereto, the word lines WL [n:0] are disconnected from the signal VWLX and are connected to the signal VNN. Accordingly, WL [n:0] become 0.0 [V]. 
         [0095]    Next, an operation for selecting a word line while in the high voltage operation will be described. 
         [0096]    The controller  18  outputs SLCT=“H” and HVXB=“L” to the LV_SLCT output circuit  20 . The controller  18  outputs HVXD=VPP=10.0 [V], VWLXD=3.0 [V], and VWLX=VPP=10.0 [V] to the level shift circuit  22 . The controller  18  outputs VWLXP=3.0 [V] and VNN=0.0 [V] to the word line selection circuit  24 . Note that, “H”=VCC=3.0 [V] and “L”=0.0 [V]. 
         [0097]    In the voltage value, SLCT of the level shift circuit  22 , HV_SLCTB of the level shift circuit  22 , and HVXPB [n:0] and XPB [n:0] of the word line selection circuit  24  are different from each other, depending on the selection of a word line WL. 
         [0098]    Hereinafter, an operation for selecting the word line WL 0  and supplying WL 0 =VPP=10.0 [V] will be described, as an example for the selecting a word line. In this case, the controller  18  outputs SLCT=“H”, HVXPB [ 0 ]=VCC=3.0 [V], XPB [ 0 ]=“L”, HVXPB [n:1]=VPP=10.0 [V], and XPB [n:1]=“H” to each circuit. Note that, n is a positive integer, and HVXPB [n:0] and XPB [n:0] correspond to n+1 lines of word lines WL. 
         [0099]    An operation of the LV_SLCT output circuit  20  will be described. The signal LV_SLCT output from the LV_SLCT output circuit  20  is fixed to LV_SLCT=VCC=3.0 [V] based on SLCT=“H” and HVXB=“L”. 
         [0100]    Next, an operation of the level shift circuit  22  will be described. Irrespective to the logical value of the signal SLCT, the PMOS transistor P 1  and the NMOS transistor N 2  are in a conductive state based on LV_SLCT=3.0 [V], HVXD=VPP=10.0 [V], VWLXD=3.0 [V], and VWLX=VPP=10.0 [V]. 
         [0101]    When the gate voltage of the DMOS transistor D 2  is equal to “H”=3.0 [V] based on SLCT=“H”, the DMOS transistor D 2  is connected to the signal VWLXD, so that the voltage of the signal HV_SLCTB is lowered. When the voltage of the signal HV_SLCTB is lowered, the driving force of the DMOS transistor D 1  connected to the signal HV_SLCTB is further lowered. At this time, in order to lower the voltage of the signal HV_SLCTB to near VWLXD=3.0 [V], the driving force of the DMOS transistor Dl is adjusted to be considerably lower than the driving force of the DMOS transistor D 2 . 
         [0102]    On the contrary, when no word line is selected, SLCT=“L” is input to the level shift circuit  22 . When the gate voltage of the DMOS transistor D 2  is “L”=0.0 [V], the DMOS transistor D 2  becomes a non-conductive state based on a source voltage=VWLXD=3.0 [V]. 
         [0103]    On the other hand, the DMOS transistor D 1  maintains the conductive state. Therefore, the signal HV_SLCTB increases up to VWLX=10.0 [V]. Thus, the level shift circuit  22  operates as a level shifter, configured by the DMOS transistors D 1  and D 2 , that shifts the voltage range of VCC=3.0 [V]/0.0 [V] to the voltage range of VPP=10.0 [V]/VCC=3.0 [V], and as an inverter circuit. Note that, a relation of HV_SLCTB becomes 3.0 [V] from SLCT=“H”=3.0 [V]. 
         [0104]    An operation of the word line selection circuit  24  will be described. All the NMOS transistors N 50 , N 51 , . . . , N 5 n, in which the inverse logic of the signal SLCT is input to the gate terminal, become a conductive state based on SLCT=“H”. Note that, since the word line WL 0  is selected, HVXPB [ 0 ] becomes 3.0 [V], XPB [ 0 ] becomes “L”, HVXPB [n:1] become VPP=10.0 [V], and XPB [n:1] become “H”. 
         [0105]    The PMOS transistors P 2 , P 30 , and P 30 A become a conductive state based on relations of HV_SLCTB=3.0 [V], HVXPB [ 0 ]=3.0 [V], and VWLXP=3.0 [V]. The NMOS transistor N 30  becomes a non-conductive state based on XPB[ 0 ]=“L”. Thus, the word line WL 0  is connected to VWLX=VPP=10.0 [V] and is disconnected from VNN=0.0 [V]. Therefore, WL 0  becomes VPP=10.0 [V]. Further, the other word lines WL 1  to WLn are disconnected from VWLX, and are connected to the signal VNN based on HVXPB [n:1]=VPP=10.0 [V] and XPB [n:1]=“H”. Therefore, WL [n:1] become 0.0 [V]. 
         [0106]    When SLCT=“H”, HVXPB [n:0]=3.0 [V], and XPB [n:0]=“L”, all the word lines WL [n:0] may be selected, as in the above-described case of the selection of the word line WL 0 . Accordingly, WL [n:0] become VPP=10.0 [V]. 
         [0107]    Next, an operation for selecting none of the word lines WL [n:0] will be described. In this case, the controller  18  outputs SLCT=“L”. For HVXPB [n:0], VPP=10.0 [V] or VCC=3.0 [V] may be input, and for XPB [n:0] an arbitrary input value of “H” or “L” may be input. 
         [0108]    By inputting SLCT=“L”, HV_SLCTB becomes 10.0 [V]. Therefore, the PMOS transistor P 2  becomes a non-conductive state. On the other hand, all the NMOS transistors N 50 , N 51 , . . . , N 5 n, into which the inverse logic of SLCT is input, become a conductive state. Thus, the word line WL [n:0] are disconnected from the signal VWLX and are connected to the signal VNN. Accordingly, WL [n:0] becomes 0.0 [V]. 
         [0109]    The row decoder  14  according to the first exemplary embodiment includes the level shift circuit  22  that shifts the voltage range so that the voltage applied to the electrodes of the PMOS transistor P 30  and the like of the word line selection circuit  24  is in the range from 0.0 [V] to VCC in the normal operation, and is not in the range from 0.0 [V] to VPP but in the range from VCC to VPP in the high voltage operation. Thus, it is not necessary for the row decoder  14  according to the first exemplary embodiment to use a high-voltage PMOS transistor for the PMOS transistor P 30  and the like, in the word line selection circuit  24 . Accordingly, in the row decoder  14  according to the first exemplary embodiment may prevent an increase in the area of a circuit, and may maintain high operation speed. 
       Second Exemplary Embodiment  
       [0110]    Next, a second exemplary embodiment of the present invention will be described. 
         [0111]      FIG. 5  is a circuit diagram illustrating a row decoder  14 A according to the second exemplary embodiment of the present invention. The row decoder  14 A according to the second exemplary embodiment is different from the row decoder  14 , described with reference to  FIG. 2  according to the first exemplary embodiment, in that a level shift circuit  30  is disposed instead of the LV_SLCT output circuit  20 . 
         [0112]    A level shift circuit  22  and a word line selection circuit  24  are the same of those of the row decoder  14 . 
         [0113]    In the level shift circuit  30 , PMOS transistors P 4  and P 5  and NMOS transistors N 6 , N 7 , and N 8  are connected, as shown in  FIG. 5 . 
         [0114]    In  FIG. 6 , the voltage values of the respective signals in normal operation (NORMAL) that uses a normal voltage when reading data, and in high voltage operation (HV) that uses a high voltage, for example, when writing or erasing data, in selection and non-selection of the word lines, are shown. In  FIG. 7A , a timing chart of the respective signals in the normal operation is shown. In  FIG. 7B , a timing chart of the respective signals in the high voltage operation is shown. 
         [0115]    First, an operation for selecting a word line in the normal operation will be described. 
         [0116]    The controller  18  outputs HVX=“L”, HVXB=“H”, and VCWX=VCW=3.6 [V] to the level shift circuit  30 . A signal VCW is a voltage which is supplied from an internal power supply (not shown). 
         [0117]    The controller  18  outputs HVXD=0.0 [V], VWLXD=0.0 [V], and VWLX=VCW=3.6 [V] to the level shift circuit  22 . 
         [0118]    The controller  18  outputs the VWLXP=0.0 [V] and the VNN=0.0 [V] to the word line selection circuit  24 . Note that, “H”=VCC=3.0 [V] and “L”=0.0 [V]. 
         [0119]    The signals SLCT and LV_SLCT of the level shift circuit  30 , the HV_SLCTB of the level shift circuit  22 , and the signals HVXPB [n:0] and XPB [n:0] of the word line selection circuit  24 , are different from each other in a voltage value, depending on the selection of a word line WL. 
         [0120]    Hereinafter, as an example for the selecting a word line, an operation for selecting the word line WL 0  and supplying WL 0 =VCW=3.6 [V] will be described. 
         [0121]    In this case, the controller  18  outputs SLCT=“H”, HVXPB [ 0 ]=0.0 [V], XPB [ 0 ]=“L”, HVXPB [n:1]=VCW=3.6 [V], and XPB [n:1]=“H” to each circuit. Note that, n is a positive integer, and HVXPB [n:0] and XPB [n:0] correspond to n+1 lines of word lines WL. 
         [0122]    Next, an operation of the level shift circuit  30  will be described. The level shift circuit  30  operates as a level shift circuit which shifts the signal from VCC=3.0 [V] to VCW=3.6 [V] based on HVX=“L” and HVXB=“H”. Accordingly, the level shift circuit  30  shifts SLCT=“H”=VCC to LV_SLCT=VCW=3.6 [V] and outputs the shifted signal to the level shift circuit  22  at the rear stage thereof. The same description of the other operations as those of the first exemplary embodiment will be omitted 
         [0123]    In  FIG. 8 , the voltage states at the portions are shown when a word line is selected in the high voltage operation. In  FIG. 9 , the voltage states at the portions are shown when no word line is selected in the high voltage operation. 
         [0124]    The row decoder  14  according to the second exemplary embodiment includes the level shift circuit  22  that shifts the voltage range, so that the voltage applied to the electrodes of the PMOS transistor P 30  and the like of the word line selection circuit  24  is in the range from 0.0 [V] to VCC, in the normal operation, and is not in the range from 0.0 [V] to VPP but in the range from VCC to VPP, in the high voltage operation. Accordingly, the row decoder  14  according to the second exemplary embodiment of the present invention is not necessary to use a high-voltage PMOS transistor for the PMOS transistor P 30  and the like of the word line selection circuit  24 . Accordingly, in the row decoder  14  according to this exemplary embodiment may prevent an increase in the area of a circuit, and may maintain a high operation speed. 
       Third Exemplary Embodiment  
       [0125]    Next, a third exemplary embodiment of the present invention will be described. 
         [0126]      FIG. 10  is a circuit diagram illustrating a row decoder  14 B according to the third exemplary embodiment of the present invention. The row decoder  14 B according to the third exemplary embodiment is different from the row decoder  14 A, described with reference to  FIG. 5  according to the second exemplary embodiment, in that the PMOS transistors P 2  of the word line selection circuit  24  are not used, and HV_SLCTB and HVXP are input to the gates and the sources of the PMOS transistors P 30 , P 31 , . . . , P 3 n, respectively. Note that the level shift circuits  30  and  22  are the same of those of the row decoder  14 A according to the second exemplary embodiment. 
         [0127]    In  FIG. 11 , the voltage values of the respective signals in normal operation (NORMAL) that uses a normal voltage when reading data, and in high voltage operation (HV) that uses a high voltage, for example, when writing or erasing data, in selection and non-selection of the word lines, are shown. 
         [0128]    First, an operation for selecting a word line in the normal operation will be described. 
         [0129]    In the selection operation in the normal operation, the controller  18  outputs HVX=“L”, HVXB=“H”, VCWX=VCW=3.6 [V] to the level shift circuit  30 . Further, the controller  18  outputs HVXD=0.0 [V], VWLXD=0.0 [V] and VWLX=VCW=3.6 [V] to the level shift circuit  22 . The controller  18  outputs VWLXP=0.0 [V] and VNN=0.0 [V] to the word line selection circuit  24 . Note that, “H”=VCC=3.0 [V] and “L”=0.0 [V]. The voltage value of SLCT and LV_SLCT of the level shift circuit  30 , the HV_SLCTB of the level shift circuit  22 , and the signals HVXP [n:0] and XPB [n:0] of the word line selection circuit  24  are different from each other due to the selection of a word line WL. 
         [0130]    Hereinafter, an operation for selecting the word line WL 0  and supplying WL 0 =VCW=3.6 [V] will be described, as an example for selecting of a word line. In this case, the controller  18  outputs SLCT=“H”, HVXP [ 0 ]=VCW=3.6 [V], XPB [ 0 ]=“L”, HVXP [n:1]=0.0 [V], and XPB [n:1]=“H” to each circuit. Note that, n is a positive integer, and HVXP [n:0] and XPB [n:0] correspond to n+1 lines of word lines WL. 
         [0131]    An operation of the level shift circuit  30  will be described. The level shift circuit  30  operates as a level shift circuit which shifts the signal from VCC=3.0 [V] to VCW=3.6 [V] based on HVX=“L” and HVXB=“H”. Accordingly, the level shift circuit  30  outputs the input SLCT=“H”=VCC as LV_SLCT=VCW=3.6 [V] to the level shift circuit  22  at the rear stage thereof. 
         [0132]    Next, an operation of the level shift circuit  22  will be described. The DMOS transistors D 1  and D 2  are always in a conductive state based on HVXD=0.0 [V], VWLXD=0.0 [V], and VWLX=VCW=3.6 [V], irrespective to the logical value of the signals SLCT and LV_SLCT. Therefore, the level shift circuit  22  operates as an inverter circuit configured by the PMOS transistor P 1  and the NMOS transistor N 1 . Accordingly, the level shift circuit  22  outputs the input LV_SLCT=3.6 [V] as HV_SLCTB=0.0 [V] to the word line selection circuit  24 . 
         [0133]    Next, an operation of the word line selection circuit  24  will be described. All the NMOS transistors N 50 , N 51 , . . . , N 5 n in which the inverse logic of SLCT is input to the gate terminals become a non-conductive state based on SLCT=“H”. Here, since the word line WL 0  is selected, HVXP [ 0 ] becomes VCW=3.6 [V], XPB [ 0 ] becomes “L”, HVXP [n:1] become 0.0 [V], and XPB [n:1] become “H”. The PMOS transistors P 30  and P 30 A become a conductive state based on HV_SLCTB=0.0 [V], HVXP [ 0 ]=3.6 [V], and VWLXP=0.0 [V]. The NMOS transistors N 30 , N 31 , . . . , N 3 n become a non-conductive state based on XPB [ 0 ]=“L”. Thus, the word line WL 0  is connected to HVXP [ 0 ]=VCW=3.6 [V] and is disconnected from VNN=0.0 [V]. Accordingly, WL 0  becomes VCW=3.6 [V]. The other word lines WL are disconnected from HVXP [n:1] and are connected to VNN based on HVXP [n:1]=0.0 [V], VWLXP=0.0 [V], and XPB [n:1]=“H”. Accordingly, WL [n:1] become 0.0 [V]. 
         [0134]    When SLCT=“H”, HVXP [n:0]=VCW=3.6 [V], and XPB [n:0]=“L”, all the word lines WL [n:0] may be selected, as in the above-described case of the selection of the word line WL 0 . Accordingly, WL [n:0] become VCW=3.6 [V]. 
         [0135]    Next, an operation for selecting none of the word lines WL [n:0] will be described. In this case, the controller  18  outputs SLCT=“L”. For HVXP [n:0], VCW=3.6 [V] or VCW=0.0 [V] may be input, and for XPB [n:0] an arbitrary input value of “H” or “L” may be input. 
         [0136]    By inputting SLCT=“L”, LV_SLCT=0.0 [V] becomes HV_SLCTB=3.6 [V]. Therefore, the PMOS transistors P 30 , P 31 , . . . , P 3 n become a non-conductive state. On the other hand, all the NMOS transistors N 50 , N 51 , . . . , N 5 n, into which the inverse logic of the signal SLCT is input, become a conductive state. Thus, since the word lines WL [n:0] are disconnected from the signal HVXP [n:0] and are connected to the VNN, WL [n:0] become 0.0 [V]. 
         [0137]    Next, an operation for selecting a word line in the high voltage operation will be described. 
         [0138]    In this operation, the controller  18  outputs HVX=“H”, HVXB=“L”, and VCWX=VCC=3.0 [V] to the level shift circuit  30 . Further, the controller  18  outputs HVXD=VPP=10.0 [V], VWLXD=3.0 [V], and VWLX=VPP=10.0 [V] to the level shift circuit  22 . Furthermore, the controller  18  outputs VWLXP=3.0 [V] and VNN=0.0 [V] to the word line selection circuit  24 . Note that, “H”=VCC=3.0 [V] and “L”=0.0 [V]. Further, in the voltage value, SLCT of the level shift circuit  30 , the signal HV_SLCTB of the level shift circuit  22 , and the signals HVXP [n:0] and XPB [n:0] of the word line selection circuit  24  are different from each other, depending on the selection of a word line WL. 
         [0139]    Hereinafter, an operation for selecting the word line WL 0  and supplying WL 0 =VPP=10.0 [V] will be described as an example for selecting a word line. In this case, the controller  18  outputs SLCT=“H”, HVXP [ 0 ]=VPP=10.0 [V], XPB [ 0 ]=“L”, HVXP [n:1]=VCC=3.0 [V], and XPB [n:1]=“H” to each circuit. Note that, n is a positive integer, and HVXP [n:0] and XPB [n:0] correspond to n+1 lines of word lines WL. 
         [0140]    An operation of the level shift circuit  30  will be described. LV_SLCT output from the level shift circuit  22  is fixed to LV_SLCT=VCC=3.0 [V] based on HVX=“H” and HVXB=“L”. 
         [0141]    Next, an operation of the level shift circuit  22  will be described. Irrespective to the logical value of SLCT, the PMOS transistor P 1  and the NMOS transistor N 2  are always in a conductive state, based on LV_SLCT=3.0 [V], HVXD=VPP=10.0 [V], VWLXD=3.0 [V], and VWLX=VPP=10.0 [V]. When the gate voltage of the DMOS transistor D 2  is equal to “H”=3.0 [V] based on SLCT=“H”, the DMOS transistor D 2  is connected to the signal VWLXD, and the voltage of the signal HV_SLCTB is lowered. When the voltage of the signal HV_SLCTB is lowered, the driving force of the DMOS transistor D 1  connected to the signal HV_SLCTB is further lowered. At this time, in order to lower the voltage of the signal HV_SLCTB to near VWLXD=3.0 [V], the driving force of the DMOS transistor D 1  is adjusted to be considerably lower than the driving force of the DMOS transistor D 2 . 
         [0142]    On the contrary, when no word line is selected, SLCT=“L” is input. When the gate voltage of the DMOS transistor D 2  is “L”=0.0 [V], the DMOS transistor D 2  becomes a non-conductive state based on a source voltage=VWLXD=3.0 [V]. 
         [0143]    On the other hand, since the DMOS transistor D 1  maintains the conductive state, the signal HV_SLCTB increases up to VWLX=10.0 [V]. Thus, the level shift circuit  22  operates as a level shifter, configured by the DMOS transistors D 1  and D 2 , that shifts the voltage range of VCC=3.0 [V]/0.0 [V] to the voltage range of VPP=10.0 [V]/VCC=3.0 [V], and as an inverter circuit. Here, SLCT=“H”=3.0 [V] is output as HV_SLCTB=3.0 [V] to the word line selection circuit  24 . 
         [0144]    Next, an operation of the word line selection circuit  24  will be described. All the NMOS transistors N 50 , N 51 , . . . , N 5 n, in which the inverse logic of the signal SLCT is input to the gate terminal, become a non-conductive state based on SLCT=“H”. Here, since the word line WL 0  is selected, the controller  18  outputs HVXP [ 0 ]=VPP=10.0 [V], XPB [ 0 ]=“L”, HVXP [n:1]=VCC=3.0 [V], and XPB [n:1]=“H” to the word line selection circuit  24 . The PMOS transistors P 30  and P 30 A become a conductive state based on relations of HV_SLCTB=3.0 [V], HVXP [ 0 ]=10.0 [V], and VWLXP=3.0 [V]. The NMOS transistors N 30 , N 31 , . . . , and N 3 n become a non-conductive state based on XPB[ 0 ]=“L”. Thus, the word line WL 0  is connected to HVXP [ 0 ]=VPP=10.0 [V] and is disconnected from VNN=0.0 [V]. Therefore, WL 0  becomes VPP=10.0 [V]. The other word lines WL 1  to WLn are disconnected from HVXP [n:1] based on HVXP [n:1]=VCC=3.0 [V], VWLXP=3.0 [V], and XPB [n:1]=“H” and are connected to the signal VNN. Therefore, WL [n:1] become 0.0 [V]. 
         [0145]    When SLCT=“H”, HVXP [n:0]=VPP=10.0 [V], and XPB [n:0]=“L”, all the word lines WL [n:0] may be selected, as in the above-described case of the selection of the word line WL 0 . Accordingly, WL [n:0] become VPP=10.0 [V]. 
         [0146]    Next, an operation for selecting none of the word lines WL [n:0] will be described. In this case, the controller  18  outputs SLCT=“L”. For HVXP [n:0], VPP=10.0 [V] or VCC=3.0 [V] may be input, and for XPB [n:0] an arbitrary input value of “H” or “L” may be input. 
         [0147]    By inputting SLCT=“L”, HV_SLCTB becomes 10.0 [V]. Therefore, the PMOS transistors P 30 , P 31 , . . . , P 3 n become a non-conductive state. On the other hand, all the NMOS transistors N 50 , N 51 , . . . , N 5 n, into which the inverse logic of SLCT is input, become a conductive state. Thus, the word lines WL [n:0] are disconnected from HVXP [n:0] and are connected to the signal. VNN. Accordingly, WL [n:0] become 0.0 [V]. 
         [0148]    In the third exemplary embodiment, the PMOS transistor P 2  of the row decoder  14 A shown in  FIG. 5  is not used. Accordingly, in the row decoder  14 B according to the third exemplary embodiment, the number of transistors may be reduced and a circuit operation may be performed at a high speed. 
       Fourth Exemplary Embodiment  
       [0149]    Next, a fourth exemplary embodiment of the present invention will be described. 
         [0150]      FIG. 12  is a circuit diagram illustrating a row decoder  14 C according to the fourth exemplary embodiment of the present invention. The row decoder  14 C according to the fourth exemplary embodiment is different from the row decoder  14 A, described with reference to  FIG. 5  according to the second exemplary embodiment, in that the DMOS transistor D 3  is connected to the DMOS transistor D 1  in parallel in the level shift circuit  22 . A level shift circuit  30  and a word line selection circuit  24  are the same as those of the row decoder  14 A. 
         [0151]    First, an operation when SLCT changes from “H” to “L” while in the normal operation, will be described. 
         [0152]    When in an equilibrium state, the voltage of HV_SLCTB becomes HV_SLCTB=0.0 [V] when SLCT is “H”, and becomes HV_SLCTB=VCW=3.6 [V] when SLCT is “L”. Accordingly, when SLCT changes from “H” to “L”, the voltage of the HV_SLCTB increases from 0.0 [V] to 3.6 [V] with a time constant. 
         [0153]    When SLCT changes from “H” to “L” in the row decoder  14 A described in the second exemplary embodiment, the DMOS transistor D 1  becomes a conductive state, and therefore, the voltage of the signal HV_SLCTB increases. However, in the fourth exemplary embodiment, since the gate terminal and the source terminal are connected to each other in the DMOS transistor D 1 , the voltage between the gate and source is always set to VGS=0.0 [V]. When SLCT is “H” in the selection operation of the word line while in the high voltage operation, the voltage of the signal HV_SLCTB is lowered to near VWLXD=3.0 [V]. Therefore, in the DMOS transistor D 1 , the driving force is adjusted to be considerably lowered when compared to the DMOS transistor D 2 . Due thereto, in the row decoder  14 A according to the second exemplary embodiment, the time constant of the signal HV_SLCTB becomes larger relatively, when the voltage increases from 0.0 [V] to 3.6 [V]. 
         [0154]    On the other hand, in the row decoder  14 C according to the fourth exemplary embodiment, the DMOS transistor D 3  is added to the row decoder  14 A and is connected to the DMOS transistor D 1  in parallel: Therefore, when SLCT is “L”, the gate terminal of the DMOS transistor D 3  becomes “H”. Accordingly, when the signal SLCT changes from “H” to “L” in the row decoder  14 C, not only the DMOS transistor D 1  but also the DMOS transistor D 3  becomes a conductive state of VGS=3.0 [V]. When SLCT is “H” in the selection operation of a word line while in the high voltage operation, the DMOS transistor. D 3  becomes a non-conductive state of VGS&lt;−3.0 [V]. Therefore, in the fourth exemplary embodiment, the driving force of the DMOS transistor D 3  is not required to be lowered than the driving force of the DMOS transistor D 2 . Thus, in the row decoder  14 C according to the fourth exemplary embodiment, the transition of HV_SLCTB (from 0.0 [V] to 3.6 [V]) may be performed at a high speed in the selection operation of a word line in the normal operation.

Technology Category: 3