Patent Publication Number: US-7724535-B2

Title: Semiconductor device, related method, and printed circuit board

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the invention relate to a semiconductor device, a method related to the semiconductor device, and a printed circuit board. In particular, embodiments of the invention relate to a semiconductor device including an impedance circuit and an AC component interrupter, a method related to the semiconductor device, and a printed circuit board comprising an impedance circuit. 
   This application claims priority to Korean Patent Application No. 10-2006-0043068, filed May 12, 2006, the subject matter of which is hereby incorporated by reference in its entirety. 
   2. Description of the Related Art 
   Semiconductor devices are used in high-speed and high-performance systems. Thus, a semiconductor device used in such a system needs a greater operating speed and a greater number of signal input and/or output terminals. In a semiconductor device, noise proportional to “N×dl/dt” (wherein “dl/dt” is a signal variation speed and “N” is the number of varying signals) is generated and induced over a power voltage or a ground voltage. This so-called “power voltage noise” may alter the perceived frequency of data/control signals or cause circuit malfunctions. Power voltage noise is proportional to the impedance of a terminal connecting element(s) internal to a semiconductor device and external element(s). Thus, power voltage noise may be generally reduced by reducing the apparent impedance of a connection terminal. One approach to reducing the impedance of any one connection terminal reduction suggests increasing the number of connection terminals provided by the semiconductor device. 
     FIG. 1  is a schematic diagram illustrating a conventional semiconductor device. The semiconductor device of  FIG. 1  includes a chip  1  and a package  2 . 
   Referring to  FIG. 1 , terminals  10 - 1  are power voltage terminals of chip  1 , terminals  10 - 2  are ground voltage terminals of chip  1 , terminals  20 - 1  are power voltage terminals of package  2 , and terminals  20 - 2  are ground voltage terminals of package  2 . Each terminal referred to herein may be a pad. In addition, VCCL is a power voltage line of chip  1 , and GNDL is a ground voltage line of chip  1 . When package  2  is a ball grid array (BGA) package, terminals  20 - 1  and  20 - 2  are balls, and when package  2  is a thin small outline package (TSOP), terminals  20 - 1  and  20 - 2  are pins. The power voltage line VCCL connects power voltage terminals  10 - 1  inside chip  1 , and ground voltage line GNDL connects ground voltage terminals  10 - 2  inside chip  1 . 
     FIG. 2  is an equivalent circuit diagram illustrating the semiconductor device of  FIG. 1 . In  FIG. 2 , “Rpkg” and “Lpkg” respectively represent a package resistance and a package inductance present in series between power voltage terminal  20 - 1  of package  2  and power voltage terminal  10 - 1  of chip  1 . In addition, “Cdie” indicates a static capacitance present between power voltage line VCCL and ground voltage line GNDL, “I” indicates an electrical current that flows from power voltage line VCCL in chip  1  to ground voltage line GNDL, and “Vn” indicates power voltage noise. 
   A parallel resonant impedance Zp of the circuit illustrated in  FIG. 2  is defined by Equation 1: 
   
     
       
         
           
             Z 
             ⁢ 
             
                 
             
             ⁢ 
             P 
           
           = 
           
             
               
                 V 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 n 
               
               I 
             
             = 
             
               
                 1 
                 
                   
                     jω 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     C 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     d 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     i 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     e 
                   
                   + 
                   
                     1 
                     
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         p 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         k 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         g 
                       
                       + 
                       
                         jω 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         L 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         p 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         k 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         g 
                       
                     
                   
                 
               
               . 
             
           
         
       
     
   
   A resonant frequency obtained using Equation 1 is 
             1     2   ⁢   π   ⁢       C   ⁢           ⁢   d   ⁢           ⁢   i   ⁢           ⁢   e   ⁢           ⁢   L   ⁢           ⁢   p   ⁢           ⁢   k   ⁢           ⁢   g           .         
Power voltage noise Vn increases as electrical current I increases, and power voltage noise Vn has a maximum level at the resonant frequency. The resonant frequency is inversely proportional to inductance Lpkg, so when inductance Lpkg decreases, power voltage noise Vn decreases as well.
 
   Accordingly, as one or more of the signal variation speed and the number of varying signals increases, electrical current I increases. Thus, power voltage noise Vn induced by the power voltage or the ground voltage also increases. In addition, when inductance Lpkg of package  2  increases, power voltage noise Vn increases. 
   However, because it is difficult to reduce the number of varying signals, power voltage noise Vn is reduced by increasing the number of power voltage terminals  20 - 1  and ground voltage terminals  20 - 2 , which reduces the impedance of the terminals and thereby reduces inductance Lpkg of package  2 . 
   However, while it is possible to increase the number of power voltage terminals  20 - 1  and ground voltage terminals  20 - 2  to reduce inductance Lpkg of package  2 , increasing the number of power voltage terminals  20 - 1  and ground voltage terminals  20 - 2  has the disadvantage of increasing the size of package  2 . That is, there is a limit to the amount that power voltage noise can be reduced by increasing the number of power voltage terminals  20 - 1  and ground voltage terminals  20 - 2 . In addition, even though inductance Lpkg of package  2  can be reduced by increasing the number of terminals  20 - 1  and  20 - 2 , increasing the number of terminals  20 - 1  and  20 - 2  shifts the resonant frequency to a frequency that is greater than an operable frequency of the semiconductor device and does not necessarily reduce the impedance at the resonant frequency. Thus, in the semiconductor device of  FIG. 1 , the power voltage noise which occurs at the resonant frequency may not be reduced. 
     FIG. 3  is a schematic diagram illustrating a conventional semiconductor device having a configuration intended to reduce power voltage noise. The semiconductor device of  FIG. 3  is substantially the same as the semiconductor device of  FIG. 1  except that the semiconductor device of  FIG. 3  includes an impedance circuit  3  disposed between a power voltage terminal  20 - 1 ′ of power voltage terminals  20 - 1  of package  2  and ground voltage GND. 
   Referring to  FIG. 3 , impedance circuit  3  is disposed outside of package  2 ; however, impedance circuit  3  may be disposed inside package  2  and may be disposed inside chip  1 . When impedance circuit  3  is disposed outside of package  2 , impedance circuit  3  may be mounted on package  2 . 
     FIG. 4  is an equivalent circuit diagram illustrating the semiconductor device illustrated in  FIG. 3 . In  FIGS. 2 and 4 , like reference symbols indicate like elements or values. In  FIG. 4 , “Rpkg 1 ” and “Lpkg 1 ” respectively denote a first package resistance and a first package inductance present in series between a power voltage terminal  20 - 1  of package  2  and a power voltage terminal  10 - 1  of chip  1 . In addition, “Rpkg 2 ” and “Lpkg 2 ” respectively denote a second package resistance and a second package inductance present in series between power voltage terminal  20 - 1 ′ of package  2  and power voltage terminal  10 - 1  of chip  1 . 
   In  FIGS. 3 and 4 , impedance circuit  3  may include a capacitor; a capacitor and a resistor connected to one another in series; or a capacitor, an inductor, and a resistor connected to one another in series. In other words, compared to the semiconductor device of  FIG. 1 , the semiconductor device of  FIG. 3  additionally includes a serial resonant circuit between a power voltage terminal  20 - 1 ′ of power voltage terminals  20 - 1  and ground voltage terminal  20 - 2 . 
   A parallel resonant impedance Zp of the circuit illustrated in  FIG. 4  is defined by Equation 1 by replacing Rpkg, Lpkg with Rpkg 1 , Lpkg 1 , respectively, and a serial resonant impedance Zs of that circuit is defined by Equation 2: 
   
     
       
         
           
             Z 
             ⁢ 
             
                 
             
             ⁢ 
             s 
           
           = 
           
             
               
                 V 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 n 
               
               I 
             
             = 
             
               
                 R 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 t 
               
               + 
               
                 
                   j 
                   ⁡ 
                   
                     ( 
                     
                       
                         ω 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         L 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         t 
                       
                       - 
                       
                         1 
                         
                           ω 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           C 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           t 
                         
                       
                     
                     ) 
                   
                 
                 . 
               
             
           
         
       
     
   
   It is assumed in Equation 2 that impedance circuit  3  includes a capacitor, an inductor, and a resistor, wherein, in Equation 2, the capacitance of the capacitor, the inductance of the inductor, and the resistance of the resistor are represented by C, L, and R, respectively. Also in Equation 2, Rt denotes Rpkg 2 +R, Ct denotes C×Cdie/C+Cdie, and Lt denotes Lpkg 2 +L. A serial resonant frequency obtained by Equation 2 is 
             1     2   ⁢   π   ⁢       C   ⁢           ⁢   t   ⁢           ⁢   L   ⁢           ⁢   t           .         
Power voltage noise Vn increases as electrical current I increases, and power voltage noise Vn has a minimum level at the serial resonant frequency. Also, because the serial resonant frequency is inversely proportional to inductance Lt, power voltage noise Vn decreases as inductance Lt decreases.
 
   Thus, the semiconductor device of  FIG. 3  reduces power voltage noise Vn by making the resonant frequency of the serial resonant circuit and the resonant frequency of the parallel resonant circuit the same and offsetting a maximum value of power voltage noise Vn obtained by resonance of the parallel resonant circuit with a minimum value of power voltage noise Vn obtained by resonance of the serial resonant circuit. That is, the semiconductor device of  FIG. 3  can reduce power voltage noise Vn by reducing the impedance at the resonant frequency. 
   Alternatively, though it is not shown, impedance circuit  3  may be disposed between a terminal  20 - 2 ′ of ground voltage terminals  20 - 2  and power voltage Vcc. In another alternative, an impedance circuit may be disposed between a terminal  20 - 1 ′ of power voltage terminals  20 - 1  of package  2  and ground voltage GND and another impedance circuit may be disposed between a terminal  20 - 2 ′ of ground voltage terminals  20 - 2  and power voltage Vcc. 
   Semiconductor devices analogous to the one illustrated in  FIG. 3  are disclosed, for example, in U.S. Pat. No. 5,926,061. 
   Although the semiconductor device of  FIG. 3  can be arranged such that it can reduce the AC component power voltage noise and such that impedance circuit  3  can reduce the impedance at the resonant frequency, the semiconductor device of  FIG. 3  has the disadvantage of having a relatively large number of terminals receiving the power voltage or the ground voltage. Thus, the semiconductor device of  FIG. 3  will suffer from a relatively large drop in the power voltage and/or ground voltage, so DC component power voltage noise will increase. 
     FIG. 5  is a schematic diagram illustrating a conventional printed circuit board (PCB). The PCB of  FIG. 5  includes a substrate  30  having a plurality of layers, a semiconductor device  32 , and decoupling capacitors  34 - 1  to  34 - 4 . Substrate  30  includes signal line layers  30 - 1  and  30 - 4 , a power voltage layer  30 - 2 , and a ground voltage layer  30 - 3 . In  FIG. 5 , the dots (“·”) each represent a connection to power voltage layer  30 - 2 , and the “×”s each represent a connection to ground voltage layer  30 - 3 . 
     FIG. 6  is an equivalent circuit illustrating the PCB of  FIG. 5 . In  FIG. 6 , “Cp” denotes a capacitance that exists in the PCB; Ll denotes an inductance between power voltage terminal  40 - 1  of substrate  30  and power voltage layer  30 - 2  of substrate  30 ; “Cd”, “Ld”, and “Rd” represent a capacitance, an inductance, and a resistance, respectively, of decoupling capacitors  34 - 1  to  34 - 4 , which are represented by element  34  in  FIG. 6 ; and “Vpn” represents the power voltage noise between power voltage line PVCCL and ground voltage line PGNDL of substrate  30 . “Rpkg”, “Lpkg”, “Cdie”, and “I” represent the same values in  FIG. 6  as in  FIG. 2 . 
   A parallel resonant impedance Za of the circuit of  FIG. 6  is defined by Equation 3: 
   
     
       
         
           
             Z 
             ⁢ 
             
                 
             
             ⁢ 
             a 
           
           = 
           
             
               
                 V 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 p 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 n 
               
               I 
             
             = 
             
               
                 1 
                 
                   
                     jω 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     C 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     p 
                   
                   + 
                   
                     1 
                     
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         d 
                       
                       + 
                       
                         j 
                         ⁡ 
                         
                           ( 
                           
                             
                               ω 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               L 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               d 
                             
                             - 
                             
                               1 
                               
                                 ω 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 C 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 d 
                               
                             
                           
                           ) 
                         
                       
                     
                   
                 
               
               + 
               
                 jω 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 L 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 1. 
               
             
           
         
       
     
   
   A resonant frequency obtained through Equation 3 is 
             1     2   ⁢   π   ⁢       C   ⁢           ⁢   d   ⁢           ⁢   L   ⁢           ⁢   d           .         
Power voltage noise Vpn increases as electrical current I increases, and power voltage noise Vpn has a maximum level at the resonant frequency. Also, since the resonant frequency is inversely proportional to inductance Ld, power voltage noise Vpn decreases as inductance Ld decreases.
 
   Thus, in order to reduce the power voltage noise induced in the conventional PCB, the decoupling capacitors are added to thereby reduce inductance Ld. When “Ci”, “Li”, and “Ri” respectively represent a capacitance, an inductance, and a resistance of each of the decoupling capacitors, and N decoupling capacitors having the same capacitance, inductance, and resistance are connected to one another in parallel, the total capacitance, inductance, and resistance of the N decoupling capacitors are N×Ci, Li/N, and Ri/N, respectively. However, while power voltage noise can be reduced by reducing the inductance by adding decoupling capacitors to the PCB, adding the decoupling capacitors shifts the resonant frequency of the PCB to a frequency that is greater than an operable frequency of the semiconductor device mounted on the PCB, so the power voltage noise at the resonant frequency of the PCB of  FIG. 5  cannot be reduced. 
   SUMMARY OF THE INVENTION 
   Embodiments of the invention provide a semiconductor device in which AC component power voltage noise is reduced and in which it is possible to prevent DC component power voltage noise from increasing, a method for reducing AC component power voltage noise and which may prevent DC component power voltage noise from increasing, and a printed circuit board (PCB) having reduced power voltage noise at the resonant frequency of the PCB. 
   In one embodiment, the invention provides a semiconductor device comprising a chip comprising a plurality of first power voltage terminals and a plurality of first ground voltage terminals, a package comprising a plurality of second power voltage terminals connected to the plurality of first power voltage terminals and a plurality of second ground voltage terminals connected to the plurality of first ground voltage terminals, wherein the chip is disposed in the package. The semiconductor device further comprises an impedance circuit connected between a DC component second power voltage terminal and a ground voltage, wherein the DC component second power voltage terminal is one of the plurality of second power voltage terminals, and an AC component interrupter connected between the DC component second power voltage terminal and a power voltage and interrupting an AC component of the power voltage. Both the AC component and a DC component of the power voltage are applied to each of the second power voltage terminals except the DC component second power voltage terminal, and the ground voltage is applied to each of the second ground voltage terminals. 
   In another embodiment, the invention provides a semiconductor device comprising a chip comprising a plurality of first power voltage terminals and a plurality of first ground voltage terminals, and a package comprising a plurality of second power voltage terminals connected to the plurality of first power voltage terminals and a plurality of second ground voltage terminals connected to the plurality of first ground voltage terminals, wherein the chip is disposed in the package. The semiconductor device further comprises a first impedance circuit connected between a DC component second ground voltage terminal and a power voltage, wherein the DC component second ground voltage terminal is one of the plurality of second ground voltage terminals, and a first AC component interrupter connected between the DC component second ground voltage terminal and a ground voltage and interrupting an AC component of the ground voltage. The AC component and a DC component of the ground voltage is provided to each of the second ground voltage terminals except the DC component second ground voltage terminal, and an AC component and a DC component of the power voltage is applied to at most each of the second power voltage terminals. 
   The semiconductor device may further comprise a second impedance circuit connected between a DC component second power voltage terminal and the ground voltage, wherein the DC component second power voltage terminal is one of the plurality of second power voltage terminals; and a second AC component interrupter connected between the DC component second power voltage terminal and the power voltage and interrupting an AC component of the power voltage, wherein only the DC component of the power voltage is provided to the DC component second power voltage terminal. 
   In yet another embodiment, the invention provides a method for reducing power voltage noise in a semiconductor device comprising a chip comprising a plurality of first power voltage terminals and a plurality of first ground voltage terminals; and a package comprising a plurality of second power voltage terminals connected to the plurality of first power voltage terminals and a plurality of second ground voltage terminals connected to the plurality of first ground voltage terminals, wherein the chip is disposed in the package. The method comprises reducing AC component power voltage noise using a first serial resonant circuit connected between a DC component second power voltage terminal and a ground voltage, wherein the DC component second power voltage terminal is one of the plurality of second power voltage terminals; and interrupting an AC component of a power voltage using a first AC component interrupter connected between the DC component second power voltage terminal and the power voltage. The method further comprises providing both the AC component and a DC component of the power voltage to each of the second power voltage terminals except the DC component second power voltage terminal; and providing both an AC component and a DC component of the ground voltage to at most each of the second ground voltage terminals. 
   In still another embodiment, the invention provides a PCB comprising a substrate comprising a power voltage layer supplying a power voltage and a ground voltage layer supplying a ground voltage; a plurality of decoupling capacitors connected between the power voltage and the ground voltage, wherein the plurality of decoupling capacitors make a resonant frequency of the PCB higher than an operable frequency of the PCB; and an impedance circuit connected between the power voltage and the ground voltage and reducing an impedance at the resonant frequency. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will be described herein with reference to the accompanying drawings. In the drawings: 
       FIG. 1  is a schematic diagram illustrating a conventional semiconductor device; 
       FIG. 2  is an equivalent circuit illustrating the semiconductor device of  FIG. 1 ; 
       FIG. 3  is a schematic diagram illustrating another conventional semiconductor device; 
       FIG. 4  is an equivalent circuit illustrating the semiconductor device of  FIG. 3 ; 
       FIG. 5  is a schematic diagram illustrating a conventional printed circuit board (PCB); 
       FIG. 6  is an equivalent circuit illustrating the PCB of  FIG. 5 ; 
       FIG. 7  is a schematic diagram illustrating a semiconductor device in accordance with an embodiment of the invention; 
       FIG. 8  is a schematic diagram illustrating a semiconductor device in accordance with another embodiment of the invention; 
       FIG. 9  is a schematic diagram illustrating a PCB in accordance with an embodiment of the invention; 
       FIG. 10  is an equivalent circuit illustrating the PCB of  FIG. 9 ; and, 
       FIG. 11  is a graph illustrating an impedance characteristic with respect to a frequency of a PCB in accordance with an embodiment of the invention. 
   

   DESCRIPTION OF EMBODIMENTS 
   Embodiments of the invention will now be described with reference to the accompanying drawings. The drawings may not be drawn to scale, and like reference symbols indicate like or similar elements throughout the drawings. 
     FIG. 7  is a schematic diagram illustrating a semiconductor device in accordance with an embodiment of the invention. The semiconductor device illustrated in  FIG. 7  is similar to the semiconductor device illustrated in  FIG. 3 , except that one of power voltage terminals  20 - 1  is a DC component power voltage terminal  20 - 1 ′, and the semiconductor device illustrated in  FIG. 7  additionally comprises an AC component interrupter  5  electrically connected between a power voltage Vcc and DC component power voltage terminal  20 - 1 ′. AC component interrupter  5  may comprise a Ferrite or an inductor. In  FIG. 7 , AC component interrupter  5  is disposed outside of the semiconductor device (i.e., outside of package  2 ); however, AC component interrupter  5  may be disposed inside package  2  and also may be disposed inside chip  1 . 
   The semiconductor device of  FIG. 7  uses AC component interrupter  5  to interrupt the AC component of power voltage Vcc and applies only the DC component of power voltage Vcc to DC component power voltage terminal  20 - 1 ′. Thus, because the DC component of power voltage Vcc is provided to the semiconductor device via DC component power voltage terminal  20 - 1 ′, the number of power voltage terminals in the semiconductor device does not decrease (relative to the device of  FIG. 1 ), so the impedance of power voltage terminals  20 - 1  (including DC component power voltage terminal  20 - 1 ′) does not increase and the level of power voltage Vcc does not drop. As a result, the power voltage noise of the DC component of power voltage Vcc does not increase. The power voltage noise of the DC component of power voltage Vcc may be referred to herein as “DC component power voltage noise.” In addition, the power voltage noise of the AC component of power voltage Vcc may be referred to herein as “AC component power voltage noise,” the ground voltage noise of the DC component of ground voltage GND may be referred to herein as “DC component ground voltage noise,” and the ground voltage noise of the AC component of ground voltage GND may be referred to herein as “AC component ground voltage noise.” 
   The conventional semiconductor device of  FIG. 3  cannot apply power voltage Vcc to the semiconductor device via DC component power voltage terminal  20 - 1 ′, so the impedance of power voltage terminals  20 - 1  increases, which leads to an increase in the DC component power voltage noise. However, in the embodiment illustrated in  FIG. 7 , the DC component of power voltage Vcc is applied to the semiconductor device via DC component power voltage terminal  20 - 1 ′, so the impedance of power voltage terminals  20 - 1  (including DC component power voltage terminal  20 - 1 ′) does not increase and the DC component power voltage noise does not increase. 
   The semiconductor device of  FIG. 7  uses impedance circuit  3  to reduce the AC component power voltage noise and uses AC component interrupter  5  to prevent the DC component power voltage noise from increasing. 
     FIG. 8  is a schematic diagram illustrating a semiconductor device in accordance with another embodiment of the invention. The semiconductor device of  FIG. 8  is similar to the semiconductor device of  FIG. 7 , except that one of ground voltage terminals  20 - 2  is a DC component ground voltage terminal  20 - 2 ′, and the semiconductor device of  FIG. 8  additionally comprises an AC component interrupter  6 . AC component interrupter  6  may comprise a Ferrite or an inductor. In addition, in the embodiment illustrated in  FIG. 8 , AC component interrupter  6  is disposed outside of the semiconductor device (i.e., outside of package  2 ); however, AC component interrupter  6  may be disposed inside package  2  and may also be disposed inside chip  1 . 
   In the semiconductor device of  FIG. 8 , AC component interrupter  6  interrupts the AC component of ground voltage GND and applies only the DC component of ground voltage GND to DC component ground voltage terminal  20 - 2 ′ (which is one of ground voltage terminals  20 - 2 ). Thus, since the DC component of ground voltage GND is applied to the semiconductor device via DC component ground voltage terminal  20 - 2 ′, the number of ground voltage terminals  20 - 2  of the semiconductor device is not reduced (relative to the device of  FIG. 1 ), so the impedance of ground voltage terminals  20 - 2  (including DC component ground voltage terminal  20 - 2 ′) does not increase and the level of ground voltage GND does not drop. As a result, it is possible to substantially prevent the DC component ground voltage noise from increasing. 
   That is, the semiconductor device of  FIG. 8  can apply ground voltage GND (i.e., the DC component of ground voltage GND) to the semiconductor device via DC component ground voltage terminal  20 - 2 ′, so the impedance of ground voltage terminals  20 - 2  (including DC component ground voltage terminal  20 - 2 ′) does not increase, and it is possible to prevent the DC component ground voltage noise from increasing. 
   The semiconductor device of  FIG. 8  not only uses impedance circuit  3  to reduce the AC component ground voltage noise, but also uses AC component interrupter  6  to prevent the DC component ground voltage noise from increasing. In an alternative embodiment of the invention, the semiconductor device of  FIG. 8  does not include AC component interrupter  5 . 
   In another embodiment of the invention, the semiconductor device of  FIG. 8  may also comprise a second impedance circuit connected between DC component ground terminal  20 - 2 ′ and power voltage Vcc. The second impedance circuit may be a serial resonant circuit and may be used to reduce AC component power voltage noise. 
   A method for reducing power voltage noise in a semiconductor device in accordance with an embodiment of the invention will now be described with reference to  FIGS. 7 and 8 . Referring to  FIG. 8 , for example, in accordance with an embodiment of the invention, the method for reducing power voltage noise in the semiconductor device illustrated in  FIG. 8  comprises reducing an AC component power voltage noise using impedance circuit  3  (i.e., a first serial resonant circuit) connected between DC component second power voltage terminal  20 - 1 ′ and ground voltage GND. DC component second power voltage terminal  20 - 1 ′ is one of the plurality of second power voltage terminals  20 - 1 . The method further comprises interrupting an AC component of power voltage Vcc using AC component interrupter  5  (i.e., a first AC component interrupter) connected between DC component second power voltage terminal  20 - 1 ′ and power voltage Vcc, providing both the AC component and a DC component of power voltage Vcc to each of second power voltage terminals  20 - 1  except DC component second power voltage terminal  20 - 1 ′, and providing both an AC component and a DC component of ground voltage GND to at most each of second ground voltage terminals  20 - 2 . Only the DC component of power voltage Vcc is provided to DC component second power voltage terminal  20 - 1 ′. The method described above may also be performed using the semiconductor device of  FIG. 7 . 
   Referring to  FIG. 8 , the method may further comprise reducing the AC component power voltage noise using a second impedance circuit (i.e., a second serial resonant circuit) connected between DC component second ground voltage terminal  20 - 2 ′ and power voltage Vcc. DC component second ground voltage terminal  20 - 2 ′ is one of the plurality of second ground voltage terminals  20 - 2 . The method may still further comprise interrupting an AC component of ground voltage GND using AC component interrupter  6  (i.e., a second AC component interrupter) connected between DC component second ground voltage terminal  20 - 2 ′ and ground voltage GND and providing only the DC component of ground voltage GND to DC component ground voltage terminal  20 - 2 ′. 
     FIG. 9  is a schematic diagram illustrating a printed circuit board (PCB) in accordance with an embodiment of the invention. The PCB of  FIG. 9  is similar to the PCB of  FIG. 5 , except that the PCB of  FIG. 9  additionally comprises an impedance circuit  36 . 
     FIG. 10  is an equivalent circuit illustrating the PCB of  FIG. 9 . Referring to  FIG. 10 , impedance circuit  36  comprises a capacitor Cs, an inductor Ls, and a resistor Rs that are connected in series. The equivalent circuit of  FIG. 10  is similar to the equivalent circuit of  FIG. 6 , except that the equivalent circuit of  FIG. 10  additionally comprises impedance circuit  36 . Impedance circuit  36  is connected to decoupling capacitors  34 - 1  to  34 - 4 , which are represented by element  34  in  FIG. 10 . Like decoupling capacitors  34 - 1  to  34 - 4 , impedance circuit  36  of the PCB of  FIG. 10  comprises a capacitor, an inductor, and a resistor connected in series. However, unlike decoupling capacitors  34 - 1  to  34 - 4 , impedance circuit  36  is adapted to lower the impedance at the resonant frequency to thereby reduce the power voltage noise at the resonant frequency of the PCB. 
   A parallel resonant impedance of the circuit illustrated in  FIG. 10  is defined by Equation 3, and a serial resonant impedance of the circuit illustrated in  FIG. 10  is defined by Equation 4: 
   
     
       
         
           
             Z 
             ⁢ 
             
                 
             
             ⁢ 
             a 
             ⁢ 
             
                 
             
             ⁢ 
             s 
           
           = 
           
             
               
                 V 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 p 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 n 
               
               I 
             
             = 
             
               
                 R 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 s 
               
               + 
               
                 
                   j 
                   ⁡ 
                   
                     ( 
                     
                       
                         ω 
                         ⁡ 
                         
                           ( 
                           
                             
                               L 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               s 
                             
                             + 
                             
                               L 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           ) 
                         
                       
                       - 
                       
                         1 
                         
                           ω 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           C 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           s 
                         
                       
                     
                     ) 
                   
                 
                 . 
               
             
           
         
       
     
   
   A serial resonant frequency obtained from Equation 4 is 
             1     2   ⁢   π   ⁢       C   ⁢           ⁢     s   ⁡     (       L   ⁢           ⁢   s     +     L   ⁢           ⁢   1       )               .         
Power voltage noise Vpn increases as electrical current I increases, and power voltage noise Vpn has a minimum level at the serial resonant frequency, and since the serial resonant frequency is inversely proportional to the inductance “Ls+L1” power voltage noise Vpn decreases as the inductance decreases.
 
   Thus, the semiconductor device of  FIG. 9  can reduce the power voltage noise at the resonant frequency by making the resonant frequency of the serial resonant circuit and the resonant frequency of the parallel resonant circuit the same and offsetting a maximum value of the power voltage noise Vpn obtained by resonance of the parallel resonant circuit with a minimum value of the power voltage noise Vpn obtained by resonance of the serial resonant circuit. That is, it is possible to reduce the impedance of power voltage terminal  40 - 1  and ground voltage terminal  40 - 2 . 
   In the PCB of  FIG. 9 , in accordance with an embodiment of the invention, the capacitor, the inductor, and the resistor of impedance circuit  36  may each be discrete components disposed on substrate  30  (i.e., disposed on the PCB). Alternatively, in the PCB of  FIG. 9 , in accordance with another embodiment of the invention, the capacitor may be a discrete component disposed on substrate  30  (i.e., disposed on the PCB), the inductor may be realized by helically arranging on signal line layer  30 - 1  or signal line layer  30 - 4  a signal line connected from at least one end of impedance circuit  36  to at least one of power voltage layer  30 - 2  and ground voltage layer  30 - 3 , and, rather than providing a discrete resistor, an amount of resistance imparted by impedance circuit  36  may be set by controlling the length and width of the helically-arranged signal line mentioned above. 
   In the PCB of  FIGS. 9 and 10 , in accordance with an embodiment of the invention, the resonant frequency of impedance circuit  36  is preferably set to a resonant frequency in a range of 0.8 fr to 1.2 fr, where “fr” is the resonant frequency of the PCB without capacitor Cs of impedance circuit  36 . 
     FIG. 11  is a graph illustrating an impedance characteristic with respect to a frequency of the PCB in accordance with an embodiment of the invention. In the graph of  FIG. 11 , the horizontal axis represents frequency, the vertical axis represents impedance, solid line CV 1  shows variation in impedance in a PCB in accordance with an embodiment of the invention, and dotted line CV 2  shows variation in impedance in a conventional PCB. It is evident from the graph of  FIG. 11  that, while the impedance of the conventional PCB at the resonant frequency is relatively high, indicating that the power voltage noise of the conventional PCB is relatively high, the impedance of the PCB in accordance with an embodiment of the invention at the resonant frequency is relatively low, indicating that the power voltage noise of the PCB in accordance with an embodiment of the invention is relatively low. In  FIG. 11 , frequency “fr” indicates the resonant frequency of the conventional PCB and the PCB in accordance with an embodiment of the invention. 
   Accordingly, a PCB in accordance with an embodiment of the invention does not simply shift the resonant frequency of the PCB to a frequency that is higher than the operable frequency of the semiconductor device by adding decoupling capacitors, but reduces the impedance at the resonant frequency to thereby reduce the power voltage noise which can occur at the resonant frequency. That is, when a PCB in accordance with an embodiment of the invention comprises the appropriate number of decoupling capacitors, the resonant frequency of the PCB will be higher than the operable frequency of a corresponding semiconductor device, and, when the resonant frequency of an impedance circuit of the PCB is appropriately adjusted, power voltage noise occurring at the resonant frequency of the PCB may be reduced. 
   A semiconductor device in accordance with an embodiment of the invention may have reduced AC component power voltage noise relative to a conventional semiconductor device and may have DC component power voltage noise that does not increase relative to a conventional semiconductor device. In addition, in accordance with the method for reducing power voltage noise in a semiconductor device in accordance with an embodiment of the invention, AC component power voltage noise may be reduced and DC component power voltage noise may be prevented from increasing. Thus, the semiconductor device in accordance with an embodiment of the invention may have improved performance. 
   Further, in accordance with an embodiment of the invention, by adding an impedance circuit to a PCB, the power voltage noise occurring at the resonant frequency of the PCB may be reduced.