Abstract:
A radio frequency (RF) device that can achieve high frequency response while maintaining high output impedance and high breakdown voltage includes a substrate, a gate, at least a dummy gate, at least a doped region, a source region and a drain region. The substrate includes a well of first type and a well of second type. The well of second type is adjacent to the well of first type.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to a radio frequency (RF) device and particularly to a radio frequency device that can achieve high frequency response while maintaining high output impedance and high breakdown voltage. 
         [0003]    2. Description of the Related Art 
         [0004]    In order to meet the increasing popularity of various wireless communication applications, demands for high-voltage radio frequency devices with high frequency response have correspondingly rapidly increased. Accordingly, with regard to the demands for high-voltage radio frequency devices, achieving high frequency response while maintaining high output impedance and high breakdown voltage is very important. Although conventional asymmetric high-voltage radio frequency devices can achieve high output impedance and high breakdown voltage, the frequency response could not be effectively improved. 
         [0005]    Referring to  FIG. 1 , a conventional high-voltage radio frequency device as illustrated in  FIG. 1  primarily includes a semiconductor substrate  100 , an n-type doped well  102 , a p-type doped region  104 , a p-type buried doped region  106 , a gate  108 , an n-type source region  110  and an n-type drain region  112 . The gate  108  includes a gate electrode and a gate dielectric layer (not labeled). The n-type doped well  102  is formed in a surface of the semiconductor substrate  100 . The buried doped region  106  is formed in the surface of the semiconductor substrate  100  and adjacent to the n-type doped well  102 . The gate  108  is directly formed on the semiconductor substrate  100  and crossing over an interface of the n-type doped well  102  and the buried doped region  106 . The n-type source region  110  is formed on a surface of the buried doped region  106  and at a side of the gate  108 . The n-type source region  110  and the n-type doped well  102  are isolated from each other by the buried doped region  106 . The p-type doped region  104  is formed on the surface of the buried doped region  106  and at a side of the n-type source region  110  far away from the gate  108 . The buried doped region  104  can be connected or disconnected to the n-type source region  110 . The n-type drain region  112  is formed in a surface of the n-type doped well  102  and at another side of the gate  108 . 
         [0006]    However, although the above-mentioned high-voltage radio frequency device can effectively improve the output impedance and breakdown voltage, since an area occupied by the gate is excessively large, it could not effectively improve frequency response. 
       BRIEF SUMMARY 
       [0007]    It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. 
         [0008]    A radio frequency device in accordance with an embodiment of the present invention includes a substrate, a gate of first type formed over the substrate, a dummy gate of first type formed on the substrate, a doped region of first type, a source region of first type and a drain region of first type. The substrate includes a well of first type and a well of second type. The well of second type is adjacent to the well of first type. The gate of first type is formed over the well of second type. The dummy gate of first type is formed over the well of first type. The drain region of first type is formed in the well of first type and adjacent to the dummy gate of the first type. The source region of first type is formed in the well of second type and adjacent to the gate of first type. The doped region of first type is formed in the well of first type and adjacent to the well of second type. 
         [0009]    A radio frequency device in accordance with another embodiment of the present invention includes a substrate, a gate of first type formed over the substrate, multiple dummy gates formed over the substrate, multiple doped regions, a source region of first type and a drain region of first type. The substrate includes a well of first type and a well of second type. The well of second type is adjacent to the well of first well. The gate of first type is formed over the well of second type. The dummy gates are formed over the well of first type. The drain region of first type is formed in the well of first type and adjacent to one of the dummy gates far away from the gate of first type. The source region of first type is formed in the well of second type and adjacent to the gate of first type. The doped regions are formed in the well of first type and between the source region of first type and the drain region of first type. 
         [0010]    A method for fabricating a radio frequency device in accordance with an embodiment of the present invention includes: providing a substrate including a well of first type and a well of second type therein, wherein the well of first type and the well of second type are formed adjacent to each other; and forming a dummy gate of first type over the well of first type, and a gate of first type over the well of second type. 
         [0011]    A method for fabricating a radio frequency device in accordance with another embodiment of the present invention includes: providing a substrate including a well of first type and a well of second type therein, wherein the well of first type and the well of second type are formed adjacent to each other; and forming a plurality of dummy gates over the well of first type, and a gate of first type over the well of second type. 
         [0012]    In the respective above-mentioned embodiments of the present invention, the dummy gate(s) is/are simultaneously formed with the gate in the same process. A material of the dummy gate(s) can be poly-silicon or metal, but not limited to these examples. A process for fabricating the dummy gate(s) can be chemical vapor deposition, metal sputtering, electroplating or other suitable process. 
         [0013]    In the respective above-mentioned embodiments of the present invention, the radio frequency device can be n-type metal-oxide-semiconductor (MOS) or p-type MOS. When the radio frequency device is n-type MOS, the first type is n-type and the second type is p-type. Whereas when the radio frequency device is p-type MOS, the first type is p-type and the second type is n-type. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
           [0015]      FIG. 1  is a schematic sectional view of a conventional high-voltage radio frequency device associated with the prior art. 
           [0016]      FIG. 2  is a schematic top view of a radio frequency device in accordance with a preferred embodiment of the present invention. 
           [0017]      FIG. 3  illustrates a schematic sectional view of the radio frequency device taken along line A-A in  FIG. 2 . 
           [0018]      FIG. 4  is a schematic top view of a radio frequency device in accordance with another embodiment of the present invention. 
           [0019]      FIG. 5  illustrates a schematic sectional view of the radio frequency device taken along line B-B in  FIG. 4 . 
           [0020]      FIG. 6  is a schematic top view of a radio frequency device in accordance with still another embodiment of the present invention. 
           [0021]      FIG. 7  illustrates a schematic sectional view of the radio frequency device taken along line C-C in  FIG. 6 . 
           [0022]      FIGS. 8A-8D  are flowcharts of a method for fabricating a radio frequency device in accordance with an embodiment of the present invention. 
           [0023]      FIGS. 9A-9D  are flowcharts of a method for fabricating a radio frequency device in accordance with another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
         [0025]      FIG. 2  is a schematic top view of a radio frequency device in accordance with a preferred embodiment of the present invention. 
         [0026]    Referring to  FIG. 3 ,  FIG. 3  illustrating a schematic sectional view of the radio frequency device taken along line A-A in  FIG. 2 . As illustrated in  FIGS. 2 and 3 , the radio frequency device includes a substrate  200 , a gate of first type  206 , a dummy gate of first type  208 , a doped region of first type  210 , a source region of first type  212  and a drain region of first type  214 . The substrate  200  includes a well of first type  202  and a well of second type  204 . The well of second type  204  is adjacent to the well of first type  202 . The gate of first type  206  includes a gate electrode and a gate dielectric layer (not labeled). The dummy gate of first type  208  includes a dummy gate electrode and a gate dielectric layer (not labeled). 
         [0027]    The gate of first type  206  is formed over the well of second type  204 . The dummy gate of first type  208  is formed over the well of first type  202 . The drain region of first type  214  is formed in the well of first type  202  and adjacent to the dummy gate of first type  208 . The source region of first type  212  is formed in the well of second type  204  and adjacent to the gate of first type  206 . The doped region of first type  210  is formed in the well of first type  202  and adjacent to the well of second type  204 . 
         [0028]    The first type for example is n-type, and the second type for example is p-type. Moreover, a width of the doped region of first type  210  for example is greater than 160 nanometers (nm), and a width of the dummy gate of first type  208  for example is greater than 90 nm. In addition, the radio frequency device for example further includes a plurality of low-doped drain (LDD) structures  209 . The LDD structures  209  are formed in the substrate  200  and at two sides of the gate of first type  206  and the dummy gate of first type  208  respectively. 
         [0029]      FIG. 4  is a schematic top view of a radio frequency device in accordance with another embodiment of the present invention. 
         [0030]    Referring to  FIG. 5 ,  FIG. 5  illustrating a schematic sectional view of the radio frequency device taken along line B-B in  FIG. 4 . As illustrated in  FIGS. 4 and 5 , the radio frequency device includes a substrate  200 , a gate of first type  206 , a plurality of dummy gates  208 , a plurality of doped regions  210 ,  218 , a source region of first type  212  and a drain region of first type  214 . The substrate  200  includes a well of first type  202  and a well of second type  204 . The well of second type  204  is adjacent to the well of first type  202 . The gate of first type  206  includes a gate electrode and a gate dielectric layer (not labeled), each of the dummy gates  208  includes a dummy gate electrode and a gate dielectric layer (not labeled). 
         [0031]    The gate of first type  206  is formed over the well of second type  204  and between the source region of first type  212  and the doped region  210 . The dummy gates  208  are formed over the well of first type  202  and between the drain region of first type  214  and the doped region  210 . The doped regions  218  are formed in the well of first type  202  and between the respective dummy gates  208 . The drain region of first type  214  is formed in the well of first type  202  at a side far away from the well of second type  204 . The source region of first type  212  is formed in the well of second type  204  at a side far away from the well of first type  202 . The doped region  210  is formed in the well of first type  202  at a side adjacent to the well of second type  204 . 
         [0032]    The first type for example is n-type, and the second type for example is p-type. The doped regions  210 ,  218  for example all are n-type doped regions or p-type doped regions. The dummy gates  208  can be n-type dummy gates, p-type dummy gates or combinations thereof. Moreover, a width of each of the doped regions  210 ,  218  for example is greater than 160 nm, and a width of each of the dummy gates  208  for example is greater than 90 nm. In addition, the radio frequency device for example further includes a plurality of LDD structures  209 . The LDD structures  209  are formed in the substrate  200  and at two sides of the gate of first type  206  and the dummy gates  208 . 
         [0033]      FIG. 6  is a schematic top view of a radio frequency device in accordance with still another embodiment of the present invention. 
         [0034]    Referring to  FIG. 7 ,  FIG. 7  illustrating a schematic sectional view of the radio frequency device taken along line C-C in  FIG. 6 . As illustrated in  FIGS. 6 and 7 , the radio frequency device includes a substrate  200 , a gate of first type  206 , a plurality of dummy gates  208 , a plurality of doped regions  210 ,  216 , a source region of first type  212  and a drain region of first type  214 . The substrate  200  includes a well of first type  202  and a well of second type  204 . The well of second type  204  is adjacent to the well of first type  202 . The gate of first type  206  includes a gate electrode and a gate dielectric layer (not labeled), each of the dummy gates  208  includes a dummy gate electrode and a gate dielectric layer (not labeled). 
         [0035]    The gate of first type  206  is formed over the well of second type  204  and between the source region of first type  212  and the doped region  210 . The dummy gates  208  are formed over the well of first type  202  and between the drain region of first type  214  and the doped region  210 . The doped regions  216  are formed in the well of first type  202  and between the respective dummy gates  208 . The drain region of first type  214  is formed in the well of first type  202  at a side far away from the well of second type  204 . The source region of first type  212  is formed in the well of second type  204  at a side far away from the well of first type  202 . The doped region  210  is formed in the well of first type  202  at a side adjacent to well of second type  204 . 
         [0036]    The first type for example is n-type, and the second type for example is p-type. The doped regions  210 ,  216  are different types of doped regions. For example, the doped region  210  is n-type doped region, the doped regions  216  are p-type doped regions; or the doped region  210  is p-type doped region, the doped regions  216  are n-type doped regions. The dummy gates  208  can be n-type dummy gates, p-type dummy gates or combinations thereof. Moreover, a width of each of the doped regions  210 ,  216  for example is greater than 160 nm, and a width of each of the dummy gates  208  for example is greater than 90 nm. In addition, the radio frequency device for example further includes a plurality of LDD structures  209 . The LDD structures  209  are formed in the substrate  200  and at two sides of the gate of first type  206  and the dummy gates  208 . 
         [0037]    A method for fabricating a radio frequency device in accordance with an embodiment of the present invention will be described below in detailed.  FIGS. 8A through 8D  shows flow charts of the method for fabricating a radio frequency device. Referring to  FIG. 8A  firstly, a substrate  200  is provided. The substrate  200  includes a well of first type  202  and a well of second type  204 . The well of first type  202  is adjacent to the well of second type  204 . Subsequently, referring to  FIG. 8B , a dummy gate of first type  208  is formed over the well of first type  202 , and a gate of first type  206  is formed over the well of second type  204 . Then, referring to  FIG. 8C , an ion implantation process  220  is performed using the gate of first type  206  and the dummy gate of first type  208  as a mast to form a plurality of LDD structures  209  in the substrate  200 . The LDD structures  209  are formed at two sides of the gate of first type  206  and the dummy gate of first type  208  respectively. After that, referring to  FIG. 8D , another ion implantation process  230  is performed to form a drain region of first type  214  in the well of first type  202  and adjacent to the dummy gate of first type  208 , to form a source region of first type  212  in the well of second type  204  and adjacent to the gate of first type  206 , and to form a doped region of first type  210  in the well of first type  202  and adjacent to the well of second type  204 . The doped region of first type  210  is formed between the gate of first type  206  and the dummy gate of first type  208 . 
         [0038]    In one embodiment, prior to performing the ion implantation process  230 , spacers may be formed on the sidewalls of the gate of first type  206  and the dummy gate of first type  208 . Then a dielectric layer is formed over the substrate  200  and the gate of first type  206  and the dummy gate of first type  208 . The first type for example is n-type, and the second type for example is p-type. Moreover, a width of the doped region of first type  210  for example is greater than 160 nm, and a width of the dummy gate of first type  208  for example is greater than 90 nm. 
         [0039]    A method for fabricating a radio frequency device in accordance with another embodiment will be described below in detailed.  FIGS. 9A through 9D  shows flow charts of the method for fabricating a radio frequency device. Referring to  FIG. 9A  firstly, a substrate  200  is provided. The substrate  200  includes a well of first type  202  and a well of second type  204 . The well of first type  202  is adjacent to the well of second type  204 . Next, referring to  FIG. 9B , a plurality of dummy gates  208  are formed over the well of first type  202 , and a gate of first type  206  is formed over the well of second type  204 . Then, referring to  FIG. 9C , an ion implantation process  220  is performed using the gate of first type  206  and the dummy gates  208  as a mask to form LDD structures  209  in the substrate  200 . The LDD structures  209  are formed at two sides of the gate of first type  206  and the dummy gates  208  respectively. After that, referring to FIG.  9 D, another ion implantation process  230  is performed to form a drain region of first type  214  in the doped well of first type  202  and adjacent to the dummy gates  208 , to form a source region of first type  212  in the well of second type  204  and adjacent to the gate of first type  206 , and to form doped regions  210 ,  218  in the well of first type  202  and adjacent to the well of second type  204 . The doped region  210  is formed in the well of first type  202  and adjacent to the well  204  of second type. The doped regions  218  are formed in the well of first type  202  and between the respective dummy gates  208 . 
         [0040]    In one embodiment, prior to performing the ion implantation process  230 , spacers may be formed on the sidewalls of the gate of first type  206  and the dummy gates  208 . Then, a dielectric layer is formed over the substrate  200 , the gate of first type  206  and the dummy gates  208 . The first type for example is n-type, and the second type for example is p-type. Moreover, a width of the doped region  210  for example is greater than 160 nm, and a width of each of the dummy gates  208  for example is greater than 90 nm. 
         [0041]    In addition, in the respective above-mentioned embodiments of the present invention, the dummy gate(s) is/are simultaneously formed together with the gate during the same process. A material of the dummy gate(s) can be poly-silicon or metal, but not limited to these samples. The process for fabricating the dummy gate(s) can be chemical vapor deposition, metal sputtering, electroplating or other suitable process. 
         [0042]    Moreover, in the respective above-mentioned embodiments of the present invention, the radio frequency device can be n-type metal-oxide-semiconductor (MOS) device or p-type MOS device. When the radio frequency device is an n-type MOS device, the first type is n-type, and the second type is p-type. Whereas, when the radio device is a p-type MOS device, the first type is p-type, and the second type is n-type. 
         [0043]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.