Patent Publication Number: US-2023156938-A1

Title: Electronic device

Description:
TECHNICAL FIELD 
     One embodiment of the present invention relates to an electronic device including a flexible display panel. 
     Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, manufacture, or a composition (a composition of matter). In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, a driving method thereof, or a manufacturing method thereof. 
     Note that in this specification and the like, a semiconductor device means an element, a circuit, a device, or the like that can function by utilizing semiconductor characteristics. For example, a semiconductor element such as a transistor or a diode is a semiconductor device. For another example, a circuit including a semiconductor element is a semiconductor device. For another example, a device provided with a circuit including a semiconductor element is a semiconductor device. 
     BACKGROUND ART 
     Mobile devices such as smartphones, tablets, electronic book readers, and notebook personal computers have been widely used. The mobile devices require a display panel that is suitable for displaying a larger amount of information. The amount of information displayed on a display panel with the same display area has increased with a reduction in the size of a pixel. In contrast, the mobile devices are also required to have flexibility as mobile devices and to have a larger display area. 
     A foldable electronic device has been proposed as a mode of a mobile device that achieves both flexibility and a large screen. As the foldable electronic device, an electronic device including two or more display panels or an electronic device using a flexible display panel has been proposed. 
     For example, Patent Document 1 discloses a structure of an electronic device using a flexible display. 
     REFERENCE 
     Patent Document 
     
         
         [Patent Document 1] Japanese Published Patent Application No. 2013-243588 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     A foldable electronic device including a flexible display panel has been proposed as a method of displaying a large amount of information and increasing the screen size in a mobile device. However, the flexible display panel has a problem of being shifted in position when folded as compared with the case where the display panel is held as a flat surface. 
     The flexible display panel also has a problem in that a wiring or the like of the display panel disconnects when great force is applied to a curved portion of the display panel. 
     In the case where the display area of the display panel is increased, the display panel has a problem of slipping off from the electronic device because of having flexibility when force is applied externally. 
     In view of the above problems, an object of one embodiment of the present invention is to provide an electronic device with a novel structure. Another object of one embodiment of the present invention is to provide a flexible display panel having a controllable radius of curvature. 
     Another object of one embodiment of the present invention is to provide an electronic device including a flexible display panel that is prevented from slipping off from the electronic device. 
     Note that the description of these objects does not preclude the existence of other objects. One embodiment of the present invention does not have to achieve all these objects. Note that other objects are apparent from and can be derived from the description of the specification, the drawings, the claims, and the like. 
     Note that the objects of embodiments of the present invention are not limited to the objects listed above. The objects listed above do not disturb the existence of other objects. Note that the other objects are objects that are not described in this section and will be described below. The objects that are not described in this section will be derived from the descriptions of the specification, the drawings, and the like and can be extracted from these descriptions by those skilled in the art. Note that one embodiment of the present invention is to solve at least one of the objects listed above and/or the other objects. 
     Means for Solving the Problems 
     One embodiment of the present invention is an electronic device including a display panel, a first component, a movable module, and a housing. The housing includes a first movable portion, a second component, and a third component. The third component includes a first space where the first component is stored. The display panel includes a flexible display portion. The display portion includes a first region, a second region, and a third region. The first region is fixed to the second component. The second region is fixed to the first component stored in the first space. The first movable portion connects the second component and the third component. The movable module has a function of holding a first angle that is formed between the second component and the third component by the first movable portion. The third region positioned between the first region and the second region has a function of forming a curved surface according to the first angle. In the electronic device, the first component slides in the first space according to the first angle. 
     In the above structure, the movable module includes a fourth component, a fifth component, a sixth component, a seventh component, an eighth component, a second movable portion, a third movable portion, a fourth movable portion, and a fifth movable portion. The fourth component is connected to the first movable portion and the fifth component. The fifth component is connected to the sixth component. The sixth component is connected to the seventh component. The seventh component is connected to the eighth component. The second movable portion controls a second angle formed by the fourth component and the fifth component. The third movable portion controls a third angle formed by the fifth component and the sixth component. The fourth movable portion controls a fourth angle formed by the sixth component and the seventh component. The fifth movable portion controls a fifth angle formed by the seventh component and the eighth component. The sixth component includes a second space where the seventh component is stored. The seventh component includes a third space where the eighth component is stored. In the electronic device, preferably, the eighth component is fixed to the third component and fixed to a surface of the third component that is different from a surface where the first space is provided. 
     In the above structure, the third component includes a structure body with a shape that projects toward the first space. The first component includes a notch region. The notch region is arranged so that the structure body with a projecting shape is positioned in the notch region. In the electronic device, preferably, the size of the notch region is the movable range of the first component that slides in the first space. 
     In the above structure, the housing further includes a ninth component. The display panel includes a fourth region where an electronic component is mounted. The second component includes an opening so that the fourth region is stored in a fifth space formed by the second component and the ninth component. In the electronic device, preferably, the opening has a first width and a second width, the first width is greater than the thickness of the display portion so that the display portion can pass through the first width, and the second width is greater than the thickness of a portion of the display portion where the electronic component is mounted so that the portion can pass through the second width. 
     In the electronic device with any of the above structures, in the case where the seventh component is not stored in the second space in the sixth component and the eighth component is not stored in the third space in the seventh component, preferably, a fourth space is formed by the fifth component, the sixth component, and the seventh component and part of the display panel is positioned in the fourth space. 
     In the electronic device with any of the above structures, in the case where the seventh component is stored in the second space in the sixth component and the eighth component is stored in the third space in the seventh component, preferably, part of each of the fourth component, the fifth component, and the sixth component is positioned parallel to the display panel and is in contact with the display panel. 
     In the electronic device with any of the above structures, preferably, the display panel includes a transistor and the transistor includes polycrystalline silicon in a semiconductor layer. 
     In the electronic device with any of the above structures, preferably, the display panel includes a transistor and the transistor includes a metal oxide in a semiconductor layer. 
     In the electronic device with each of the above structures, preferably, the display panel includes a transistor and the transistor includes a back gate. 
     Effect of the Invention 
     One embodiment of the present invention can provide an electronic device with a novel structure. Another embodiment of the present invention can provide a flexible display panel having a controllable radius of curvature. Another embodiment of the present invention can provide an electronic device including a flexible display panel that is prevented from slipping off from the electronic device. 
     Note that the effects of one embodiment of the present invention are not limited to the effects listed above. The effects listed above do not disturb the existence of other effects. Note that the other effects are effects that are not described in this section and will be described below. The other effects that are not described in this section will be derived from the descriptions of the specification, the drawings, and the like and can be extracted from these descriptions by those skilled in the art. Note that one embodiment of the present invention is to have at least one effect of the effects listed above and/or the other effects. Therefore, one embodiment of the present invention does not have the effects listed above in some cases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS.  1 (A) and  1 (B)  are a cross-sectional view and a development view illustrating an electronic device. 
         FIGS.  2 (A) and  2 (B)  are a cross-sectional view and a development view illustrating an electronic device. 
         FIGS.  3 (A) to  3 (D)  are cross-sectional views illustrating an electronic device. 
         FIGS.  4 (A) and  4 (B)  are cross-sectional views illustrating an electronic device. 
         FIGS.  5 (A) to  5 (E)  are cross-sectional views illustrating an electronic device. 
         FIGS.  6 (A) to  6 (C)  are a top view and development views illustrating an electronic device. 
         FIGS.  7 (A) to  7 (C)  are a top view and development views illustrating an electronic device. 
         FIGS.  8 (A) to  8 (C)  are a top view and development views illustrating an electronic device. 
         FIGS.  9 (A) to  9 (C)  are a top view and development views illustrating an electronic device. 
         FIGS.  10 (A) and  10 (B)  are a top view and a development view of a display device. 
         FIG.  11    is a cross-sectional view of a display panel. 
         FIG.  12    is a cross-sectional view of a display panel. 
         FIG.  13    is a cross-sectional view of a display panel. 
         FIGS.  14 (A) to  14 (C)  are a block diagram and circuit diagrams of a display panel. 
         FIGS.  15 (A) to  15 (D)  are circuit diagrams and a timing chart of a display panel. 
         FIG.  16    is a diagram illustrating an electronic device. 
         FIG.  17    is a diagram illustrating a housing. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments will be described with reference to the drawings. Note that the embodiments can be implemented with many different modes, and it is readily understood by those skilled in the art that modes and details thereof can be changed in various ways without departing from the spirit and scope the present invention. Thus, the present invention should not be interpreted as being limited to the following descriptions of the embodiments. 
     In the drawings, the size, the layer thickness, or the region is exaggerated for clarity in some cases. Thus, they are not always limited to the illustrated scale. Note that the drawings are schematic views illustrating ideal examples, and embodiments of the present invention are not limited to shapes or values shown in the drawings. 
     Note that the ordinal numbers used in this specification, such as “first”, “second”, and “third”, are used in order to avoid confusion among components, and the terms do not limit the components numerically. 
     Also in this specification, the terms for explaining arrangement, such as “over” and “under”, are used for convenience to describe the positional relation between components with reference to drawings. The positional relation between components is changed as appropriate in accordance with a direction in which each component is described. Thus, the positional relation is not limited to that described with a term used in this specification and can be explained with the other terms as appropriate depending on the situation. 
     In this specification and the like, a transistor is an element having at least three terminals, a gate, a drain, and a source. The transistor has a channel region between the drain (a drain terminal, a drain region, or a drain electrode) and the source (a source terminal, a source region, or a source electrode), and can make current flow between the source and the drain through the channel formation region. Note that in this specification and the like, a channel region refers to a region through which current mainly flows. 
     The functions of a source and a drain might be switched when a transistor of opposite polarity is employed or a direction of current flow is changed in circuit operation, for example. Therefore, the terms “source” and “drain” can be switched in this specification and the like. 
     In this specification and the like, “electrically connected” includes the case where components are connected through an “object having any electric function”. Here, there is no particular limitation on the “object having any electric function” as long as electric signals can be transmitted and received between the connected components. Examples of the “object having any electric function” include a switching element such as a transistor, a resistor, an inductor, a capacitor, and other elements with a variety of functions as well as an electrode and a wiring. 
     In this specification and the like, “parallel” indicates a state where two straight lines are placed at an angle greater than or equal to −10° and less than or equal to 10°. Accordingly, the case where the angle is greater than or equal to −5° and less than or equal to 5° is also included. Moreover, “perpendicular” indicates a state where two straight lines are placed at an angle greater than or equal to 80° and less than or equal to 100°. Accordingly, the case where the angle is greater than or equal to 85° and less than or equal to 95° is also included. 
     In this specification and the like, the term “film” and the term “layer” can be interchanged with each other. For example, the term “conductive layer” can be changed into the term “conductive film” in some cases. Also, the term “insulating film” can be changed into, for example, the term “insulating layer” in some cases. 
     Embodiment 1 
     In this embodiment, an electronic device including a flexible display panel will be described with reference to  FIG.  1    to  FIG.  9   . 
     The electronic device includes a flexible display panel, a first component, a movable module, and a foldable housing. The foldable housing includes a first movable portion, a second component, and a third component. In the following description, the first movable portion, the second component, and the third component are collectively referred to as a housing for simplicity unless otherwise specified. Note that the first movable portion connects the second component and the third component and can further control the angle formed by the second component and the third component. For example, a hinge or the like is preferably used as the first movable portion. 
     The housing can hold at least a first state or a second state. For example, in the first state, the housing is folded and two different display regions of the display panel are in contact with each other or display directions of display portions of the display panel face each other. In the second state, the housing is opened to have a flat display panel and the display portions perform display in the same direction. Note that the third state of the housing is a state between the first state and the second state. That is, in the third state, part of the display portions is curved and held. Note that the third state is described in detail in  FIG.  3    or  FIG.  4   . In the first state, i.e., in the case where the two different display regions of the display panel are in contact with each other or the display directions of the display portions of the display panel face each other, the display panel is not seen by a user. Thus, no display data is preferably displayed on the display panel. 
     The third component preferably includes a first space where the first component is stored. 
     The display panel includes a flexible display portion, which includes a first region, a second region, and a third region. The second component is fixed to the first region and the first component stored in the third component is fixed to the second region. Note that the first component is preferably capable of sliding in the first space of the third component without being fixed in that storage space. Note that the first region and the second component, or the second region and the first component are fixed to each other with an organic resin layer. The organic resin layer preferably functions as an adhesive layer. 
     Next, the movable module is described. The movable module can hold a first angle that is formed between the second component and the third component by the first movable portion. The third region positioned between the first region and the second region is capable of forming a curved surface according to the first angle. The position of the display panel is shifted according to the first angle by the distance where the first component slides in the first space. 
     The movable module includes a fourth component, a fifth component, a sixth component, a seventh component, an eighth component, a second movable portion, a third movable portion, a fourth movable portion, and a fifth movable portion. The fourth component is connected to the first movable portion and the fifth component. The fifth component is connected to the sixth component. The sixth component is connected to the seventh component. The seventh component is connected to the eighth component. The second movable portion can control a second angle that is formed between the fourth component and the fifth component. The third movable portion can control a third angle that is formed between the fifth component and the sixth component. The fourth movable portion can control a fourth angle that is formed between the sixth component and the seventh component. The fifth movable portion can control a fifth angle that is formed between the seventh component and the eighth component. 
     Note that the sixth component includes a second space where the seventh component is stored, and the seventh component includes a third space where the eighth component is stored. The eighth component is fixed to the third component and fixed to a surface of the third component that is different from a surface where the first space is provided. Note that the second space may be formed by providing a notch region in the sixth component. The third space may be formed by providing a notch region in the seventh component. 
     Furthermore, the third component preferably includes a structure body with a shape that projects toward the first space. The first component includes a notch region, which is arranged so that the structure body with a projecting shape is positioned in the notch region. That is, the size of the notch region is the movable range of the first component that slides in the first space. 
     The housing further includes a ninth component. The display panel includes a fourth region where an electronic component is mounted. The second component includes an opening. The opening allows the display panel in the fourth region to be stored in a fifth space formed by the second component and the ninth component. The opening preferably has a first width and a second width. The first width is preferably greater than the thickness of the display portion so that the display portion can pass through the first width. The second width is preferably greater than the thickness of a portion of the display portion where the electronic component is mounted so that the portion can pass through the second width. Note that the fifth space preferably stores a battery, a printed board on which an electronic component is mounted, or the like. An electronic component mounted on the fourth region is preferably an FPC, a driver IC, a connector, or the like. The electronic component mounted on the fourth region is preferably electrically connected to the printed board on which a plurality of electronic components are mounted. The printed board preferably has flexibility. 
     In the case where the display panel has flexibility, the display panel can be curved with a radius of curvature r that is limited by a material used for the display panel, the film thickness, or the like. Hence, the radius of curvature r of the display panel needs to be controlled so as not to be smaller than or equal to the minimum radius of curvature (hereinafter referred to as a radius of curvature r in some cases) with which the display panel can be curved without being broken. 
     First, the case where the movable module holds the first state is described. In the case where the seventh component is not stored in the second space in the sixth component and the eighth component is not stored in the third space in the seventh component, a fourth space is formed by the fifth component, the sixth component, and the seventh component. Therefore, in the first state, part of the display panel is preferably positioned in the fourth space. 
     In the first state, the third region of the display panel can be stored in the fourth space so that the radius of curvature of the display panel is not smaller than r. Thus, in the case where the first state is held, the third region can be controlled by the movable module so as not to have a radius of curvature smaller than r. When the third region is stored in the fourth space so that the radius of curvature of the display panel is not smaller than r, a wiring, an inorganic film, an organic film, an organic resin film, or the like of the display panel can be prevented from being broken. 
     Next, the case where the movable module holds the second state is described. In the case where the seventh component is stored in the second space in the sixth component and the eighth component is stored in the third space in the seventh component, the display panel is positioned parallel to part of each of the fourth component, the fifth component, and the sixth component. Alternatively, the display panel is preferably in contact with part of each of the fourth component, the fifth component, and the sixth component. 
     That is, part of each of the fourth component, the fifth component, and the sixth component preferably has a surface that supports the display panel. Note that another part of the sixth component, the seventh component, and the eighth component are preferably arranged on a back surface of the third component and have a surface positioned parallel to the third component. 
     Note that the side of the third component where the first component is arranged is referred to as a surface of the third component and the side of the third component where the eighth component is fixed is referred to as a back surface of the third component. 
     Next, an electronic device  10  is described in detail with reference to  FIG.  1    to  FIG.  9   . 
       FIG.  1 (A)  shows a cross-sectional view of the electronic device  10  as an example. The electronic device  10  includes a display panel  11 , a component  24 , a movable module  30 , and a housing. Note that in  FIG.  17   , components of the housing are denoted by solid lines.  FIG.  17    is a diagram illustrating the components of the housing. A housing  27  shown in  FIG.  17    includes a movable portion  26 , a component  20 , a component  20   a , a component  21 , a component  22 , and a component  23 . 
     The movable portion  26  includes a component  25 , a component  25   a , a component  25   b , components  25   c , and components  25   d . The component  25   a  and the component  25   b  are rotatable around the component  25 . The component  20  is fixed to the component  25   a  with the components  25   c , and the component  22  is fixed to the component  25   b  with the components  25   d . That is, the movable portion  26  functions as a first hinge. For example, a screw and the like can be used as the components  25   c  and the components  25   d . Alternatively, the component  20  and the component  25   a  may be integrally formed. Similarly, the component  22  and the component  25   b  may be integrally formed. 
     The component  22  includes a first space  22   a  where the component  24  is stored. The display panel  11  includes a flexible display portion. The display portion includes a display region  11   a , a display region  11   b , and a display region  11   c . The display region  11   a  is fixed to the component  20   a . The display region  11   b  is fixed to the component  24  stored in the component  22 . The component  24  is preferably capable of sliding in the first space  22   a  of the component  22  without being fixed in the first space  22   a . The display region  11   a  and the component  20   a , or the display region  11   b  and the component  24  are fixed to each other with an organic resin layer. The organic resin layer can function as an adhesive layer. 
     Note that the component  20   a , the display panel  11 , and the component  21  are preferably overlapped in this order in part of the display region  11   a . The component  22 , the component  24 , the display panel  11 , and the component  23  are preferably overlapped in this order in part of the display region  11   b . That is, the component  21  and the component  23  are arranged so as to surround the display regions  11   a ,  11   b , and  11   c  and function as a bezel of the display panel  11 . 
     The movable module  30  can hold a first angle that is formed between the component  20   a  and the component  22  by the movable portion  26 . The display region  11   c  positioned between the display region  11   a  and the display region  11   b  forms a curved surface according to the first angle. The position of the display panel is shifted according to the first angle by the distance where the component  24  slides in the first space  22   a.    
     Next, a structure of the movable module  30  is described in detail with reference to a development view in  FIG.  1 (B) . The movable module  30  includes a component  30   a , a component  31   a , a component  32   a , a component  33   a , a component  34   a , a movable portion  30   b , a movable portion  31   b , a movable portion  32   b , and a movable portion  33   b.    
     The component  30   a  is connected to the movable portion  26  and the component  31   a . The component  31   a  is connected to the component  32   a . The component  32   a  is connected to the component  33   a . The component  33   a  is connected to the component  34   a.    
     The movable portion  30   b  controls a second angle that is formed between the component  30   a  and the component  31   a . The movable portion  31   b  controls a third angle that is formed between the component  31   a  and the component  32   a . The movable portion  32   b  controls a fourth angle that is formed between the component  32   a  and the component  33   a . The movable portion  33   b  controls a fifth angle that is formed between the component  33   a  and the component  34   a.    
     The component  32   a  includes a space  32   c  where the component  33   a  is stored. The component  33   a  includes a space  33   c  where the component  34   a  is stored. The component  34   a  is fixed to the component  22  and fixed to a surface of the component  22  that is different from the surface where the space  22   a  is provided, with a component  34   b . In the following description, for simplicity, the side of the component  22  where the component  24  is arranged is referred to as a surface of the component  22  and the side of the component  22  where the component  34   a  is fixed is referred to as a back surface of the component  22  in some cases. Note that the space  32   c  may be formed by providing a notch region in the component  32   a . The space  33   c  may be formed by providing a notch region in the component  33   a.    
     Furthermore, the component  22  preferably includes a structure body  22   b  with a shape that projects toward the first space  22   a . The component  24  includes a notch region  24   a , which is arranged so that the structure body  22   b  is positioned in the notch region  24   a . The size of the notch region  24   a  is the movable range of the component  24  that slides in the first space  22   a . Note that  FIG.  5    illustrates the relation among the first angle, the notch region  24   a , and the structure body  22   b , and  FIG.  6    illustrates details of the structure body  22   b  and the notch region  24   a  with reference to the top view of the electronic device  10 . 
     Next, the structure of the electronic device  10  is described in detail with reference to  FIG.  2   .  FIG.  2 (A)  is a cross-sectional view of the housing  27  that holds the second state. In  FIG.  2 (A) , the display panel includes a region  11   d  as an example. Note that the display panel is formed in a region where the region  11   d , the display region  11   a , the display region  11   c , and the display region  11   b  are connected in this order. The component  20   a  includes an opening  20   s   1  so that the region  11   d  is stored in a fifth space formed by the component  20   a  and the component  21 . The display panel  11  has flexibility. Note that the display region  11   c  needs to be controlled so as not to be curved with a radius of curvature smaller than the minimum radius of curvature r of the display panel. Thus, the component  20  preferably includes a sixth space  20   s   2  where the display region of the region  11   d  is to be stored. In addition, a component  21   a  and a component  21   b  preferably include a seventh space  21   s  where the display panel  11  is stored. The display panel  11  may be provided so as to be in contact with the component  21   a  and the component  21   b  in the seventh space  21   s  or part of the component  21   a  or the component  21   b  may have a region that is not in contact with the display panel  11 . 
     For example, in the case where the component  21   a  and the component  21   b  are provided so as to be in contact with the display panel  11 , the display panel  11  is stably fixed by the component  21   a  and the component  21   b . In contrast, when part of the component  21   a  or part of the component  21   b  has a region that is not in contact with the display panel  11 , variations in processing of the display panel  11  can be absorbed by the seventh space  21   s . For example, even in the case where the display panel in the region  11   d  varies in thickness, the seventh space  21   s  can prevent the display panel  11  from being pressed and disconnected. 
     The opening  20   s   1  preferably has a first width and a second width, which will be described in detail in  FIG.  8   . The first width is preferably greater than the thickness of the display portion of the display panel  11  so that the display portion can pass through the first width. The second width is preferably greater than the thickness of a portion of the region  11   d  where an electronic component is mounted so that the portion can pass through the second width. Although not shown in the drawings, the fifth space preferably stores a battery, a printed board on which an electronic component is mounted, or the like. An electronic component  50  mounted on the region  11   d  is preferably an FPC, a driver IC, a connector, or the like, and is preferably electrically connected to the printed board on which the electronic component is mounted. The printed board preferably has flexibility. 
       FIG.  2 (B)  shows a development view of components used in the electronic device  10 . In  FIG.  2 (A) , the electronic component  50  is arranged on the side of the display panel  11  that is different from the display direction; in  FIG.  2 (B) , an electronic component  51  is arranged on the same side as the display surface of the display panel  11  unlike in  FIG.  2 (A) . That is, a terminal portion in the region  11   d  may be provided on the display surface or the surface different from the display surface. Note that the arrangement is preferably determined as appropriate in accordance with the arrangement of the battery or the printed board on which the electronic component is mounted in the fifth space. 
     In  FIG.  2 (B) , the width of the display region  11   c  is preferably greater than a distance πr. When the width of the display region  11   c  is greater than the distance πr, the contact between the component  21   a  and the component  23  can be prevented at the time when the housing  27  changes from the first state to the second state. Note that π represents pi and the radius of curvature r is a positive value excluding 0. 
     Next, the process where the electronic device  10  changes from the first state to the second state through the third state is described with reference to  FIG.  3    and  FIG.  4   . First, operations of the movable portion  26  (see  FIG.  1   ), the movable portion  30   b , the movable portion  31   b , the movable portion  32   b , and the movable portion  33   b  are defined as follows. The angle formed between the component  20   a  and the component  22  by the movable portion  26  is denoted as a first angle M 1 . The angle formed between the component  30   a  and the component  31   a  by the movable portion  30   b  is denoted as a second angle M 2 . The angle formed between the component  31   a  and the component  32   a  by the movable portion  31   b  is denoted as a third angle M 3 . The angle formed between the component  32   a  and the component  33   a  by the movable portion  32   b  is denoted as a fourth angle M 4 . The angle formed between the component  33   a  and the component  34   a  by the movable portion  33   b  is denoted as a fifth angle M 5 . 
     First, the first state where the housing  27  of the electronic device  10  is folded is described with reference to  FIG.  3 (A) . In  FIG.  3   , description is made focusing on the movable module  30 . Note that  FIG.  3 (D)  is an enlarged view of the movable module  30  in  FIG.  3 (A) . 
     In the case where the housing  27  holds the first state, the component  33   a  is not stored in the space  32   c  in the component  32   a  and the component  34   a  is not stored in the space  33   c  in the component  33   a . Note that in the case where the housing  27  holds the first state, the second angle M 2  is preferably almost a right angle. 
     In the case where the housing  27  holds the first state, preferably, a fourth space  60  is formed by the component  31   a , the component  32   a , and the component  33   a  and part of the display panel  11  is positioned inside the fourth space  60  as shown in  FIG.  3 (D) . 
     Note that in the case where the housing  27  holds the first state, the display region  11   c  can be stored in the fourth space  60  so that the radius of curvature of the display panel  11  is not smaller than r. Thus, in the case where the housing  27  holds the first state, the display region  11   c  of the display panel  11  can be controlled by the movable module  30  so as not to have a radius of curvature smaller than r. That is, when the display panel  11  is stored in the fourth space  60  so as not to be curved with a radius of curvature smaller than r, the wiring, the inorganic film, the organic film, the organic resin film, or the like of the display panel  11  can be prevented from being broken. The display region  11   a  is preferably fixed to the component  20   a  in order that the display region  11   c  can be stored in the fourth space  60  more efficiently. The display region  11   c  can be efficiently stored in the fourth space  60  when the display panel  11  is fixed to the component  20   a  up to the vicinity of the movable portion  26 . 
     Next, the case where the first angle M 1  is approximately 45° (including 45°) is shown in  FIG.  3 (B)  as an example. It is preferable that in  FIG.  3 (B) , the second angle M 2  hold almost a right angle. The third angle M 3  becomes larger, and the fourth angle M 4  and the fifth angle M 5  become smaller. The third angle M 3  to the fifth angle M 5  change when the second angle M 2  holds almost a right angle. Note that in the case where the second angle M 2  is not almost a right angle, the third angle M 3  to the fifth angle M 5  change in a way different from the above. 
     Next, the case where the first angle M 1  is almost a right angle (including a right angle) is shown in  FIG.  3 (C)  as an example. The second angle M 2  in  FIG.  3 (C)  is preferably larger than that in  FIG.  3 (B) . The third angle M 3  becomes smaller, and the fourth angle M 4  and the fifth angle M 5  become larger. The third angle M 3  to the fifth angle M 5  change when the second angle M 2  is smaller than that in  FIG.  3 (B) . Note that in the case where the second angle M 2  becomes small, the third angle M 3  to the fifth angle M 5  change in a way different from the above. 
     Next, the case where the first angle M 1  is approximately 135° (including 135°) is shown in  FIG.  4 (A)  as an example. The second angle M 2  in  FIG.  4 (A)  is preferably still larger than that in  FIG.  3 (C) . The third angle M 3  becomes larger, and the fourth angle M 4  and the fifth angle M 5  become smaller. The third angle M 3  to the fifth angle M 5  change when the second angle M 2  is larger than that in  FIG.  3 (C) . 
     Lastly, the case where the first angle M 1  is approximately 180° (including 180°) is shown in  FIG.  4 (B)  as an example. That is, the housing  27  is changed into the second state. In  FIG.  4 (B) , the second angle M 2  is still larger than that in  FIG.  4 (A)  and reaches the maximum angle. The maximum angle denotes approximately 180°. The third angle M 3  also reaches the maximum angle. The fourth angle M 4  and the fifth angle M 5  become smaller to reach the minimum angle. The minimum angle denotes approximately 0° (including 0°). Thus, the component  33   a  is stored in the component  34   a  and the component  32   a  is stored in the component  33   a . Parts of the component  30   a , the component  31   a , and the component  32   a  are in contact with the display panel  11  and can support the display panel  11 . Furthermore, it is preferable that another part of the component  32   a , the component  33   a , or the component  34   a  be in contact with the back surface of the component  22  or have a surface positioned parallel to the component  22 . 
     Note that the housing  27  is in the third state in  FIG.  3 (B) or  3 (C)  or  FIG.  4 (A) . When the housing  27  is in the second state or the third state, display data can be displayed on the display regions  11   a  to  11   c.    
     Although the first angle M 1  of the housing  27  is approximately 0°, approximately 45°, approximately 90°, approximately 135°, or approximately 180° in  FIG.  3    or  FIG.  4   , the first angle M 1  is not limited to the above examples. Any one of the angles of approximately 0° to approximately 180° can be held as the first angle. 
     Next, the relation among the first angle M 1 , the notch region  24   a  in the component  24 , and the structure body  22   b  with a projecting shape in the component  22  is described in  FIGS.  5 (A) to  5 (E) . Note that in  FIG.  5   , the movable portion  26 , the structure body  22   b , the notch region  24   a , and the first space  22   a  are described. Note that in  FIG.  5   , description is made focusing on a position Pna, which is the closest to the movable portion  26 , the position including the structure body  22   b , and a position Pnb, which is the farthest from the movable portion  26  in the first space  22   a . Note that n is a positive integer greater than or equal to 1. 
     Note that the size and the width of the component  24  are not changed. The position of the notch region  24   a  provided in the component  24  is not changed either. Furthermore, the position where the structure body  22   b  with a projecting shape is provided in the component  22  is not changed. The structure body  22   b  has a shape with a width  51  from the center of the structure body  22   b . The structure body has a semicircular cross section in the example in the drawing, but the shape is not limited and may be a pillar or the like. The structure body  22   b  preferably includes a region shared by part of the component  22 . For example, the structure body  22   b  may be simultaneously formed when the first space  22   a  is processed in the component  22 . A reduction in the number of components can reduce component costs for an electronic device. Note that in the case where the component  24  includes the structure body with a projecting shape, the notch region may be included in the component  22 . 
       FIG.  5 (A)  illustrates the case where the housing  27  holds the first state, i.e., the first angle M 1  is approximately 0°. The component  22  includes the first space  22   a  where the component  24  is stored and the component  24  can slide in the first space  22   a . Note that the component  24  is fixed to the display region  11   b , and when the first angle M 1  of the housing  27  changes, the position of the display region  11   c  is shifted and the display region  11   b  moves. That is, the display region  11   b  moves according to the distance of the position shift, and the component  24  slides according to the distance where the display region  11   b  moves. Note that the display region  11   a  is preferably fixed to the component  20   a  in the range up to a position L 1 . For the positional relation among the display regions  11   a ,  11   b , and  11   c ,  FIG.  5 (E)  can be referred to. 
     In the case where the housing  27  holds the first state, a curved surface of the display region  11   c  is preferably controlled so as not to have a radius of curvature smaller than the minimum radius of curvature r. For example, in the case where the display region  11   a  and the display region  11   b  are in contact with or face each other, the display region  11   c  forms a curved surface with a radius of curvature greater than r. Hence, part of the display region  11   b  is arranged apart from the display region  11   a  by two times the radius of curvature r (diameter) or more. That is, when the display region  11   c  forms a curved surface with a radius of curvature greater than or equal to r, the positions of part of the display region  11   b  and the display region  11   c  are shifted. 
     In the case where the housing  27  holds the first state, the distance of the position shift is the same as the distance where the component  24  stored in the first space  22   a  slides. Thus, the movable module  30  can control the display region  11   c  so as not to have a radius of curvature smaller than r. In addition, the structure body  22   b  with a projecting shape in the component  22  is in contact with a side surface of the notch region  24   a  in the component  24  that is farther from the movable portion  26 , which limits the range where the component  24  can slide toward the movable portion  26 . Furthermore, the position of the first space  22   a  is preferably determined so that the range where the component  24  can slide is limited at a position P 1   a  that is the closest to the movable portion  26 . The control of the range where the component  24  can slide allows controlling of the display panel  11  so as not to have a radius of curvature smaller than r. Note that the component  24  to which the display region  11   b  and the display region  11   b  are fixed preferably slides to the position P 1   a  close to the movable portion  26  and a position P 1   b.    
     Next, the case where the first angle M 1  changes from approximately 0° to approximately 45° is described in  FIG.  5 (B) . As for the position shift generated in the display panel  11 , the position of the display panel  11  changes according to the first angle M 1 . In the case where the first angle M 1  changes from approximately 0° to approximately 45°, the display region  11   b  and the display region  11   c  slide to move a distance d. Note that the component  24  to which the display region  11   b  and the display region  11   b  are fixed slides from the position P 1   a  to a position P 2   a  in a position close to the movable portion  26  and slides from the position P 1   b  to a position P 2   b  in a position far from the movable portion  26 . 
     Next, the case where the first angle M 1  changes from approximately 0° to approximately 90° is described in  FIG.  5 (C) . In the case where the first angle M 1  changes from approximately 0° to approximately 90°, the display region  11   b  and the display region  11   c  slide to move a distance  2   d . Note that the component  24  to which the display region  11   b  and the display region  11   b  are fixed slides from the position P 1   a  to a position P 3   a  in a position close to the movable portion  26  and slides from the position P 1   b  to a position P 3   b  in a position far from the movable portion  26 . 
     Next, the case where the first angle M 1  changes from approximately 0° to approximately 135° is described in  FIG.  5 (D) . In the case where the first angle M 1  changes from approximately 0° to approximately 135°, the display region  11   b  and the display region  11   c  slide to move a distance  3   d . Note that the component  24  to which the display region  11   b  and the display region  11   b  are fixed slides from the position P 1   a  to a position P 4   a  in a position close to the movable portion  26  and slides from the position P 1   b  to a position P 4   b  in a position far from the movable portion  26 . 
     Note that in the case where the first angle M 1  is greater than approximately 90° and less than approximately 180°, the position shift from the position L 1  occurs in some cases. This is because the display panel  11  has flexibility and thus stress is applied in such a direction that the display panel  11  is apart from the movable portion  26  with the position L as a base point. 
     Next, the case where the first angle M 1  changes from approximately 0° to approximately 180° is described in  FIG.  5 (E) . That is, when the first angle M 1  reaches approximately 180°, the housing  27  reaches the second state. In the case where the first angle M 1  changes from approximately 0° to approximately 180°, the display region  11   b  and the display region  11   c  slide to move a distance  4   d . Note that the display region  11   b  and the component  24  to which the display region  11   b  is fixed slide from the position P 1   a  to a position P 5   a  in a position close to the movable portion  26  and slide from the position P 1   b  to a position P 5   b  in a position far from the movable portion  26 . When the first angle M 1  reaches approximately 180°, the display panel  11  forms a flat surface. Thus, the position shift generated in each of  FIGS.  5 (A) to  5 (D)  all disappears. 
     Then, details of the electronic device  10  are described in  FIG.  6   . Note that description is made on a top view of the electronic device  10  in  FIG.  6 (A) , a development view of the movable module  30  in  FIG.  6 (B) , and a cross-sectional view of the electronic device  10  in  FIG.  6 (C) . Note that the description of components denoted by the same reference numerals in  FIG.  6    to  FIG.  9    is omitted. 
     First, the top view of the electronic device  10  is described with reference to  FIG.  6 (A) .  FIG.  6 (A)  is the top view of the electronic device  10  illustrated in  FIG.  2 (A) . The component  20 , the component  20   a , the component  21   a , the component  21   b , the component  22 , and the component  23  can each be fixed with a plurality of fixing units  40 . For example, a screw or the like is used as the fixing unit  40 , in which case two or more components can be easily fixed. Note that a plurality of components may be formed as one component. Effects such as simplification of assembly process and a reduction in the number of components can be obtained. 
     The movable portion  26  is constituted by the component  25 , the component  25   a , and the component  25   b , the component  25   a  is fixed to the component  20 , and the component  25   b  is fixed to the component  22 . Note that the movable portion  26  is preferably arranged outside both ends of the movable module  30 ; alternatively, the movable module  30  may be arranged outside both ends of the movable portion  26 . 
     The component  23 , the component  21   a , and the component  21   b  function as bezels. Note that in the case where the display panel  11  has flexibility, the display panel  11  can be prevented from slipping off from the bezels when having a region where the component  22 , the component  24 , the display region  11   b  of the display panel  11 , and the component  23  are overlapped in this order and when the display region  11   b  is fixed to the component  24 . 
     Since  FIG.  6 (B)  has the same structure as the movable module  30  illustrated in  FIG.  1 (B) , detailed description thereof is omitted. Note that the component  34   a  only needs to be connected to part of the component  33   a ; as an example, the component  34   a  is fixed to the component  33   a  in two regions in  FIG.  6 (A) . Note that the movable portion  30   b , the movable portion  31   b , the movable portion  32   b , and the movable portion  33   b  are preferably connected with a hinge or the like. For example, the movable portion  30   b  is fixed to the component  30   a  and the component  31   a  in two regions. The movable portion  31   b  is fixed to the component  31   a  and the component  32   a  in two regions. The movable portion  32   b  is fixed to the component  32   a  and the component  33   a  in two regions. The movable portion  33   b  is fixed to the component  33   a  and the component  34   a  in two regions. 
     For  FIG.  6 (C) , the description of the electronic device  10  illustrated in  FIG.  2 (A)  can be referred to. The component  20   a  includes the opening  20   s   1  so that the region  11   d  is stored in the fifth space formed by the component  20  and the component  20   a . The component  21   b  is preferably in contact with the display panel  11 , the component  21   a , and the component  20 . 
       FIG.  7 (A)  illustrates an electronic device  10 A, which is different from the electronic device in  FIG.  6 (A) . In  FIG.  7 (A) , the component  21  is formed as one component. A reduction in the number of components can reduce the number of fixing units  40  and the number of assembly steps. Note that the component  20   a  includes the opening  20   s   1  so that the region  11   d  is stored in the fifth space formed by the component  20  and the component  20   a . The component  21  is preferably in contact with the display panel  11  and the component  20   a.    
       FIG.  7 (C)  includes the opening  20   s   1  with a width through which the electronic component  50  can pass. Note that the component  21  is preferably arranged at a position overlapping with the opening  20   s   1 . 
       FIG.  8 (A)  illustrates an electronic device  10 B, which is different from the electronic device in  FIG.  7 (A) . In  FIG.  8 (A) , the component  20   a  includes an opening  20   s   3  so that the region  11   d  is stored in the fifth space formed by the component  20  and the component  20   a . The component  21  is preferably in contact with the display panel  11  and the component  20   a . Note that in  FIG.  8   , the component  21  is shown as a transmissive component. 
     The opening  20   s   3  preferably has a first width through which a thickness S 3  of the display portion of the display panel  11  passes and a second width S 4  through which the thickness of the electronic component  50  passes. Note that a plurality of second widths can be provided. When the opening  20   s   3  has the first width S 3  and the second width S 4 , the display panel  11  can be supported by a large area of the component  20   a . In addition, the second width S 4  can facilitate the assembly of the electronic device  10 B even after the electronic component  50  is mounted on the display panel  11 . 
       FIG.  9 (A)  illustrates an electronic device  10 C, which is different from the electronic device in  FIG.  7 (A) . In  FIG.  9 (A) , the component  20   a  includes an opening  20   s   4 .  FIG.  9 (C)  illustrates details of the opening  20   s   4 . 
     In the electronic device  10 C, an electronic component  52  mounted on the region  11   d  is arranged in the opening  20   s   4 . Note that the display panel  11  is electrically connected to an electronic component  53  through the electronic component  52 . For example, a connector or the like can be used as the electronic component  52  or the electronic component  53 . Since the display panel  11  is electrically connected to the electronic component  53  through the electronic component  52 , the region  11   d  does not need to have a curved surface. When the curved surface is not included, the control of the radius of curvature can be omitted. In addition, the adhesion between the display panel  11  and the component  21  can be improved. Furthermore, the assembly of the electronic device  11 C can be facilitated. 
     A foldable electronic device with a novel structure can be provided with use of  FIG.  1    to  FIG.  9   . In the electronic device, the radius of curvature of a flexible display panel can be controlled. As a method for controlling the radius of curvature of the display panel, the display panel partly slides by using the movable module  30  and the component  24 , so that the display panel can move a distance that is the same as the position shift generated when the display panel has a curved surface. It is thus possible to prevent the display panel from being broken by stress applied on the curved surface of the display panel. It is also possible to provide an electronic device including a flexible display panel that is prevented from slipping off from the electronic device. 
     The structures and methods described in this embodiment can be used in appropriate combination with the structures and methods described in the other embodiments. 
     Embodiment 2 
     In this embodiment, an example of the display panel illustrated in the above embodiment will be described. 
     Structure Example 
       FIG.  10 (A)  shows a top view of a display panel  700 . The display panel  700  includes a first substrate  701  and a second substrate  705  that are attached to each other with a sealant  712 . In addition, over the first substrate  701 , a pixel portion  702 , a source driver  704 , and a gate driver  706  are provided in a region sealed with the first substrate  701 , the second substrate  705 , and the sealant  712 . Furthermore, a plurality of display elements are provided in the pixel portion  702 . 
     A portion of the first substrate  701  that does not overlap with the second substrate  705  is provided with a terminal portion  708  to which an FPC  716  (FPC: Flexible printed circuit) is connected. The FPC  716  supplies a variety of signals and the like to the pixel portion  702 , the source driver  704 , and the gate driver  706  through the terminal portion  708  and a signal line  710 . 
     A plurality of gate drivers  706  may be provided. In addition, each of the gate driver  706  and the source driver  704  may be formed separately over a semiconductor substrate or the like and may be in the form of a packaged IC chip. The IC chip can be mounted over the first substrate  701  or on the FPC  716 . Note that the IC chip can be mounted on a surface (back surface) different from a display surface of the pixel portion  702  on which display data is displayed. 
     The pixel portion  702 , the source driver  704 , and the gate driver  706  can include transistors. 
     Examples of the display element provided in the pixel portion  702  include a liquid crystal element and a light-emitting element. As the liquid crystal element, a transmissive liquid crystal element, a reflective liquid crystal element, a transflective liquid crystal element, or the like can be used. Examples of the light-emitting element include self-luminous elements such as a micro LED (Light Emitting Diode), an OLED (Organic LED), a QLED (Quantum-dot LED), and a semiconductor laser. Moreover, a MEMS (Micro Electro Mechanical Systems) shutter element, an optical interference type MEMS element, or a display element using a microcapsule method, an electrophoretic method, an electrowetting method, an Electronic Liquid Powder (registered trademark) method, or the like can also be used, for example. 
       FIG.  10 (B)  shows a connection between the FPC  716  and the terminal portion  708  included in the display panel  700  shown in  FIG.  10 (A) . In  FIG.  10 (B) , with use of a through electrode, the terminal portion  708  can be exposed on the back surface direction of the pixel portion  702  on which display data is displayed. The terminal portion  708  and the FPC  716  are connected with an anisotropic conductive film containing a conductive particle CP with a diameter of approximately 3 μm. A driver IC, a connector, or the like may be connected to the terminal portion  708 . 
     Cross-Sectional Structure Example 
     Structures using a liquid crystal element or an EL element as a display element are described below with reference to  FIG.  11    to  FIG.  13   . Note that  FIG.  11    to  FIG.  13    are each a cross-sectional view taken along the dashed-dotted line Q-R in  FIG.  10 (A) .  FIG.  11    and  FIG.  12    each illustrate a structure using a liquid crystal element as a display element, and  FIG.  13    illustrates a structure using an EL element. 
     [Description on Common Portions in Display Panels] 
     The display panel  700  shown in  FIG.  11    to  FIG.  13    includes a lead wiring portion  711 , the pixel portion  702 , the source driver  704 , and the terminal portion  708 . The lead wiring portion  711  includes the signal line  710 . The pixel portion  702  includes a transistor  750  and a capacitor  790 . The source driver  704  includes a transistor  752 .  FIG.  12    illustrates the case where the capacitor  790  is not provided. 
     As an example, the transistor  750  and the transistor  752  each include a metal oxide in a semiconductor layer that is highly purified and in which formation of oxygen vacancies is inhibited. The transistors can each have a low off-state current. Accordingly, an electrical signal such as an image signal can be held for a longer time, and the interval between writings can also be set longer in a power on state. Therefore, the frequency of refresh operations can be reduced, producing an effect of reducing power consumption. Hereinafter, a transistor including a metal oxide in a semiconductor layer is referred to as an OS transistor. 
     The transistors used in this embodiment can have comparatively high field-effect mobility and thus are capable of high-speed operation. For example, when such transistors capable of high-speed operation are used in a display panel, a switching transistor in a pixel portion and a driver transistor used in a driver circuit portion can be formed over one substrate. 
     That is, a semiconductor device formed with a silicon wafer or the like is not additionally needed as a driver circuit; thus, the number of components of the semiconductor device can be reduced. Moreover, when the transistors capable of high-speed operation are used also in the pixel portion, a high-quality image can be provided. 
     Note that transistors with a variety of modes can be used as the transistors. Thus, there is no limitation on the type of transistors used. For example, it is possible to use a thin film transistor (TFT) including a non-single-crystal semiconductor film typified by amorphous silicon, polycrystalline silicon, microcrystalline (also referred to as microcrystal or semi-amorphous) silicon, or the like. The use of the TFT has various advantages. For example, since the TFT can be manufactured at a temperature lower than that of the case of using single crystal silicon, manufacturing costs can be reduced or a larger manufacturing apparatus can be used. Since a larger manufacturing apparatus can be used, TFTs can be manufactured over a large substrate. This enables a large number of display panels to be manufactured at a time, reducing the manufacturing costs. In addition, a low manufacturing temperature allows the use of a low heat-resistance substrate. Thus, transistors can manufactured over a transparent substrate (a light-transmitting substrate). The transmission of light in a display element can be controlled by the transistors over the substrate. Alternatively, part of films of the transistors can transmit light because of their thin thicknesses. Accordingly, the aperture ratio can be improved. 
     Note that when a catalyst (e.g., nickel) is used in the formation of polycrystalline silicon, crystallinity can be further improved and a transistor having excellent electrical characteristics can be formed. As a result, a gate driver circuit (a scan line driver circuit), a source driver circuit (a signal line driver circuit), and a signal processing circuit (e.g., a signal generation circuit, a gamma correction circuit, or a DA converter circuit) can be integrally formed over a substrate. 
     Note that when a catalyst (e.g., nickel) is used in the formation of microcrystalline silicon, crystallinity can be further improved and a transistor having excellent electrical characteristics can be formed. In that case, crystallinity can be improved by just performing heat treatment without performing laser irradiation. As a result, a gate driver circuit (a scan line driver circuit) and part of a source driver circuit (e.g., an analog switch) can be integrally formed over a substrate. Note that when laser irradiation for crystallization is not performed, unevenness in crystallinity of silicon can be reduced. Therefore, images with improved quality can be displayed. 
     Note that it is possible to form polycrystalline silicon or microcrystalline silicon without a catalyst (e.g., nickel). 
     Note that although the crystallinity of silicon is preferably improved to polycrystal, microcrystal, or the like in the whole panel, the present invention is not limited to this. The crystallinity of silicon may be improved only in a partial region of the panel. Selective increase in crystallinity can be achieved by selective laser light irradiation or the like. For example, only a peripheral circuit region excluding pixels may be irradiated with laser light. Alternatively, only a region of a gate driver circuit, a source driver circuit, or the like may be irradiated with laser light. Alternatively, only part of a source driver circuit (e.g., an analog switch) may be irradiated with laser light. Accordingly, the crystallinity of silicon can be improved only in a region in which a circuit needs to operate at high speed. Because a pixel region is not particularly needed to operate at high speed, the pixel circuit can operate without any problem even if the crystallinity is not improved. Since the crystallinity only needs to be improved in a small region, manufacturing steps can be decreased, throughput can be increased, and manufacturing costs can be reduced. In addition, the number of necessary manufacturing apparatuses is reduced, resulting in lower manufacturing costs. 
     The capacitor  790  shown in  FIG.  11    and  FIG.  13    includes a lower electrode formed by processing the same film as that for the semiconductor layer of the transistor  750  and reducing the resistance, and an upper electrode formed by processing the same conductive film as that for a source electrode or a drain electrode. Furthermore, two insulating films covering the transistor  750  are provided between the lower electrode and the upper electrode. That is, the capacitor  790  has a stacked-layer structure in which the insulating films functioning as dielectric films are interposed between a pair of electrodes. 
     A planarization insulating film  770  is provided over the transistor  750 , the transistor  752 , and the capacitor  790 . 
     As the transistor  750  included in the pixel portion  702  and the transistor  752  included in the source driver  704 , transistors having different structures may be used. For example, a top-gate transistor may be used as one of the transistors and a bottom-gate transistor may be used as the other. Note that the source driver  704  described above may be replaced with a gate driver circuit portion. 
     The signal line  710  is formed using the same conductive film as that for the source electrodes and the drain electrodes of the transistors  750  and  752 , and the like. Here, a low-resistance material such as a material containing a copper element is preferably used, in which case signal delay or the like due to wiring resistance can be reduced and display on a large screen is possible. 
     The terminal portion  708  includes a connection electrode  760 , an anisotropic conductive film  780 , and the FPC  716 . The connection electrode  760  is electrically connected to a terminal of the FPC  716  through the anisotropic conductive film  780 . Here, the connection electrode  760  is formed using the same conductive film as that for the source electrodes and the drain electrodes of the transistors  750  and  752 , and the like. 
     As the first substrate  701  and the second substrate  705 , a glass substrate or a flexible substrate such as a plastic substrate can be used, for example. 
     On the second substrate  705  side, a light-blocking film  738 , a coloring film  736 , and an insulating film  734  that is in contact with these films are provided. 
     Structure Example of Display Panel Using Liquid Crystal Element 
     The display panel  700  shown in  FIG.  11    includes a liquid crystal element  775 . The liquid crystal element  775  includes a conductive layer  772 , a conductive layer  774 , and a liquid crystal layer  776  provided therebetween. The conductive layer  774  is provided on the second substrate  705  side and has a function of a common electrode. In addition, the conductive layer  772  is electrically connected to the source electrode or the drain electrode of the transistor  750 . The conductive layer  772  is formed over the planarization insulating film  770  and functions as a pixel electrode. 
     For the conductive layer  772 , a material having a visible-light-transmitting property or a material having a visible-light-reflecting property can be used. An oxide material containing indium, zinc, tin, or the like is preferably used as the light-transmitting material, for example. A material containing aluminum, silver, or the like is preferably used as the reflective material, for example. 
     When a reflective material is used for the conductive layer  772 , the display panel  700  is a reflective liquid crystal display panel. On the other hand, when a light-transmitting material is used for the conductive layer  772 , the display panel  700  is a transmissive liquid crystal display panel. In the case of a reflective liquid crystal display panel, a polarizing plate is provided on the viewer side. On the other hand, in the case of a transmissive liquid crystal display panel, a pair of polarizing plates are provided such that the liquid crystal element is sandwiched therebetween. 
     The display panel  700  shown in  FIG.  12    is an example of using the liquid crystal element  775  in a horizontal electric field mode (e.g., an FFS mode). The conductive layer  774  functioning as a common electrode is provided over the conductive layer  772  with an insulating layer  773  therebetween. The alignment state of the liquid crystal layer  776  can be controlled by an electric field generated between the conductive layer  772  and the conductive layer  774 . 
     In  FIG.  12   , a storage capacitor can be composed of a stacked-layer structure of the conductive layer  774 , the insulating layer  773 , and the conductive layer  772 . Therefore, it is not necessary to provide a capacitor separately, increasing the aperture ratio. 
     Although not shown in  FIG.  11    and  FIG.  12   , an alignment film in contact with the liquid crystal layer  776  may be provided. Furthermore, an optical member (an optical substrate) such as a polarizing member, a retardation member, or an anti-reflection member and a light source such as a backlight or a side light can be provided as appropriate. 
     For the liquid crystal layer  776 , thermotropic liquid crystal, low-molecular liquid crystal, high-molecular liquid crystal, polymer dispersed liquid crystal, polymer network liquid crystal, ferroelectric liquid crystal, anti-ferroelectric liquid crystal, or the like can be used. In the case of employing a horizontal electric field mode, liquid crystal exhibiting a blue phase for which an alignment film is not used may be used. 
     As the mode of the liquid crystal element, a TN (Twisted Nematic) mode, a VA (Vertical Alignment) mode, an IPS (In-Plane-Switching) mode, an FFS (Fringe Field Switching) mode, an ASM (Axially Symmetric aligned Micro-cell) mode, an OCB (Optical Compensated Birefringence) mode, an ECB (Electrically Controlled Birefringence) mode, a guest-host mode, or the like can be used. 
     [Display Panel Using Light-Emitting Element] 
     The display panel  700  shown in  FIG.  13    includes a light-emitting element  782 . The light-emitting element  782  includes the conductive layer  772 , an EL layer  786 , and a conductive film  788 . The EL layer  786  contains an organic compound or an inorganic compound such as a quantum dot. 
     Examples of materials that can be used for an organic compound include a fluorescent material and a phosphorescent material. Examples of materials that can be used for a quantum dot include a colloidal quantum dot material, an alloyed quantum dot material, a core-shell quantum dot material, and a core quantum dot material. 
     In the display panel  700  shown in  FIG.  13   , an insulating film  730  covering part of the conductive layer  772  is provided over the planarization insulating film  770 . Here, the light-emitting element  782  is a top-emission light-emitting element including the light-transmitting conductive film  788 . Note that the light-emitting element  782  may have a bottom-emission structure in which light is emitted to the conductive layer  772  side or a dual-emission structure in which light is emitted to both the conductive layer  772  and the conductive film  788 . 
     The coloring film  736  is provided in a position overlapping with the light-emitting element  782 , and the light-blocking film  738  is provided in a position overlapping with the insulating film  730  and in the lead wiring portion  711  and the source driver  704 . The coloring film  736  and the light-blocking film  738  are covered with the insulating film  734 . A space between the light-emitting element  782  and the insulating film  734  is filled with a sealing film  732 . Note that a structure without the coloring film  736  may also be employed in the case where the EL layer  786  is formed into an island shape for each pixel or a stripe shape for each pixel column, i.e., formed by separate coloring. 
     Structure Example of Display Panel Provided with Input Device 
     An input device may be provided in the display panel  700  shown in  FIG.  11    to  FIG.  13   . Examples of the input device include a touch sensor. 
     For example, a variety of types such as a capacitive type, a resistive type, a surface acoustic wave type, an infrared type, an optical type, and a pressure-sensitive type can be used for the sensor. Alternatively, a combination of two or more of these types may be employed. 
     Note that examples of a touch panel structure include a so-called in-cell touch panel in which an input device is formed inside a pair of substrates, a so-called on-cell touch panel in which an input device is formed over the display panel  700 , and a so-called out-cell touch panel in which an input device is attached to the display panel  700 . 
     At least part of the structure examples, the drawings corresponding thereto, and the like illustrated in this embodiment can be implemented in appropriate combination with the other structure examples, the other drawings, and the like. 
     At least part of this embodiment can be implemented in appropriate combination with the other embodiments described in this specification. 
     Embodiment 3 
     In this embodiment, a display panel will be described with reference to  FIG.  14   . 
     The display panel shown in  FIG.  14 (A)  includes a pixel portion  702 , a driver circuit portion  504 , protection circuits  791 , and a terminal portion  707 . Note that a structure in which the protection circuits  791  are not provided may be employed. 
     An OS transistor can be used as transistors included in the pixel portion  702  and the driver circuit portion  504 . An OS transistor can also be used in the protection circuits  791 . 
     The pixel portion  702  includes a plurality of pixel circuits  501  that drive a plurality of display elements arranged in X rows and Y columns (X and Y each independently represent a natural number of 2 or more). 
     The driver circuit portion  504  includes driver circuits such as a gate driver  706  that outputs a scan signal to gate lines GL_ 1  to GL X and a source driver  704  that supplies a data signal to data lines DL_ 1  to DL_Y. The gate driver  706  includes at least a shift register. The source driver  704  is formed using a plurality of analog switches, for example. Alternatively, the source driver  704  may be formed using a shift register or the like. 
     The terminal portion  707  refers to a portion provided with terminals for inputting power, control signals, image signals, and the like to the display panel from external circuits. 
     The protection circuit  791  is a circuit that makes, when a potential out of a certain range is supplied to a wiring connected to the protection circuit  791 , the wiring and another wiring be in a conduction state. The protection circuit  791  shown in  FIG.  14 (A)  is connected to, for example, a variety of wirings such as scan lines GL, which are wirings between the gate driver  706  and the pixel circuits  501 , and data lines DL, which are wirings between the source driver  704  and the pixel circuits  501 . 
     The gate driver  706  and the source driver  704  may be provided over the same substrate as the pixel portion  702 , or a substrate where a gate driver circuit or a source driver circuit is separately formed (e.g., a driver circuit board formed using a single crystal semiconductor film or a polycrystalline semiconductor film) may be mounted on the substrate by COG or TAB (Tape Automated Bonding). 
     The plurality of pixel circuits  501  shown in  FIG.  14 (A)  can have a configuration shown in  FIG.  14 (B) or  14 (C) , for example. 
     The pixel circuit  501  shown in  FIG.  14 (B)  includes a liquid crystal element  570 , a transistor  550 , and a capacitor  560 . In addition, a data line DL_n, a scan line GL_m, a potential supply line VL, and the like are connected to the pixel circuit  501 . 
     The potential of one of a pair of electrodes of the liquid crystal element  570  is set in accordance with the specifications of the pixel circuit  501  as appropriate. The alignment state of the liquid crystal element  570  is set depending on written data. Note that a common potential may be supplied to one of the pair of electrodes of the liquid crystal element  570  included in each of the plurality of pixel circuits  501 . Alternatively, a potential supplied to one of the pair of electrodes of the liquid crystal element  570  in the pixel circuit  501  may differ between rows. 
     The pixel circuit  501  shown in  FIG.  14 (C)  includes transistors  552  and  554 , a capacitor  562 , and a light-emitting element  572 . In addition, the data line DL_n, the scan line GL_m, a potential supply line VL_a, a potential supply line VL_b, and the like are connected to the pixel circuit  501 . 
     Note that a high power supply potential VDD is supplied to one of the potential supply line VL_a and the potential supply line VL_b, and a low power supply potential V SS  is supplied to the other. Current flowing through the light-emitting element  572  is controlled in accordance with the potential supplied to a gate of the transistor  554 , so that the luminance of light emitted from the light-emitting element  572  is controlled. 
     At least part of the structure examples, the drawings corresponding thereto, and the like illustrated in this embodiment can be implemented in appropriate combination with the other structure examples, the other drawings, and the like. 
     At least part of this embodiment can be implemented in appropriate combination with the other embodiments described in this specification. 
     Embodiment 4 
     A pixel circuit including a memory for correcting gray levels displayed by pixels and a display panel including the pixel circuit will be described below. 
     [Circuit Configuration] 
       FIG.  15 (A)  shows a circuit diagram of a pixel circuit  400 . The pixel circuit  400  includes a transistor Tr 1 , a transistor Tr 2 , a capacitor C 1 , and a circuit  401 . In addition, a wiring S 1 , a wiring S 2 , a wiring G 1 , and a wiring G 2  are connected to the pixel circuit  400 . 
     In the transistor Tr 1 , a gate is connected to the wiring G 1 , one of a source and a drain is connected to the wiring S 1 , and the other is connected to one electrode of the capacitor C 1 . In the transistor Tr 2 , a gate is connected to the wiring G 2 , one of a source and a drain is connected to the wiring S 2 , and the other is connected to the other electrode of the capacitor C 1  and the circuit  401 . 
     The circuit  401  is a circuit including at least one display element. A variety of elements can be used as the display element, and typically, a light-emitting element such as an organic EL element or an LED element, a liquid crystal element, a MEMS (Micro Electro Mechanical Systems) element, or the like can be employed. 
     A node connecting the transistor Tr 1  and the capacitor C 1  is denoted as N 1 , and a node connecting the transistor Tr 2  and the circuit  401  is denoted as N 2 . 
     In the pixel circuit  400 , the potential of the node N 1  can be retained when the transistor Tr 1  is turned off. The potential of the node N 2  can be retained when the transistor Tr 2  is turned off. When a predetermined potential is written to the node N 1  through the transistor Tr 1  with the transistor Tr 2  being in an off state, the potential of the node N 2  can be changed in accordance with displacement of the potential of the node N 1  owing to capacitive coupling through the capacitor C 1 . 
     Here, an OS transistor can be used as one or both of the transistor Tr 1  and the transistor Tr 2 . Accordingly, the potentials of the node N 1  and the node N 2  can be retained for a long time owing to an extremely low off-state current. Note that in the case where the period in which the potential of each node is retained is short (specifically, the case where the frame frequency is higher than or equal to 30 Hz, for example), a transistor using a semiconductor such as silicon may be used. 
     Driving Method Example 
     Next, an example of a method for operating the pixel circuit  400  is described with reference to  FIG.  15 (B) .  FIG.  15 (B)  is a timing chart of the operation of the pixel circuit  400 . 
     Note that here, for simplification of description, the influence of a variety of resistance such as wiring resistance, the parasitic capacitance of a transistor, a wiring, and the like, the threshold voltage of a transistor, and the like is not taken into consideration. 
     In the operation shown in  FIG.  15 (B) , one frame period is divided into a period T 1  and a period T 2 . The period T 1  is a period in which a potential is written to the node N 2 , and the period T 2  is a period in which a potential is written to the node N 1 . 
     [Period T 1 ] 
     In the period T 1 , a potential for turning on the transistor is supplied to both the wiring G 1  and the wiring G 2 . In addition, a potential V ref  that is a fixed potential is supplied to the wiring S 1 , and a first data potential V w  is supplied to the wiring S 2 . 
     The potential V ref  is supplied from the wiring S 1  to the node N 1  through the transistor Tr 1 . The first data potential V w  is supplied to the node N 2  through the transistor Tr 2 . Accordingly, a potential difference V w -V ref  is retained in the capacitor C 1 . 
     [Period T 2 ] 
     Next, in the period T 2 , a potential for turning on the transistor Tr 1  is supplied to the wiring G 1 , and a potential for turning off the transistor Tr 2  is supplied to the wiring G 2 . A second data potential V data  is supplied to the wiring S 1 . The wiring S 2  may be supplied with a predetermined constant potential or brought into a floating state. 
     The second data potential V data  is supplied to the node N 1  through the transistor Tr 1 . At this time, capacitive coupling due to the capacitor C 1  changes the potential of the node N 2  by a potential dV in accordance with the second data potential V data . That is, a potential that is the sum of the first data potential V w  and the potential dV is input to the circuit  401 . Note that although the potential dV is shown as having a positive value in  FIG.  15 (B) , it may have a negative value. In other words, the potential V data  may be lower than the potential V ref . 
     Here, the potential dV is roughly determined by the capacitance of the capacitor C 1  and the capacitance of the circuit  401 . In the case where the capacitance of the capacitor C 1  is sufficiently higher than the capacitance of the circuit  401 , the potential dV is a potential close to the second data potential V data . 
     As described above, a potential to be supplied to the circuit  401  including the display element can be generated by a combination of two kinds of data signals in the pixel circuit  400 , so that gray levels can be corrected in the pixel circuit  400 . 
     The pixel circuit  400  can also generate a potential exceeding the maximum potential that can be supplied to the wiring S 1  and the wiring S 2 . For example, in the case of using a light-emitting element, high-dynamic range (HDR) display or the like can be performed. In the case of using a liquid crystal element, overdriving or the like can be achieved. 
     APPLICATION EXAMPLES 
     Example Using Liquid Crystal Element 
     A pixel circuit  400 LC shown in  FIG.  15 (C)  includes a circuit  401 LC. The circuit  401 LC includes a liquid crystal element LC and a capacitor C 2 . 
     One electrode of the liquid crystal element LC is connected to the node N 2  and one electrode of the capacitor C 2 , and the other electrode is connected to a wiring supplied with a potential V com2 . The other electrode of the capacitor C 2  is connected to a wiring supplied with a potential V com1 . 
     The capacitor C 2  functions as a storage capacitor. Note that the capacitor C 2  can be omitted when not needed. 
     In the pixel circuit  400 LC, a high voltage can be supplied to the liquid crystal element LC; thus, high-speed display can be performed by overdriving or a liquid crystal material with a high drive voltage can be employed, for example. In addition, gray levels can also be corrected in accordance with the operating temperature, the degradation state of the liquid crystal element LC, or the like by supply of a correction signal to the wiring S 1  or the wiring S 2 . 
     Example Using Light-Emitting Element 
     A pixel circuit  400 EL shown in  FIG.  15 (D)  includes a circuit  401 EL. The circuit  401 EL includes a light-emitting element EL, a transistor Tr 3 , and the capacitor C 2 . 
     In the transistor Tr 3 , a gate is connected to the node N 2  and one electrode of the capacitor C 2 , one of a source and a drain is connected to a wiring supplied with a potential V H , and the other is connected to one electrode of the light-emitting element EL. The other electrode of the capacitor C 2  is connected to a wiring supplied with a potential V com . The other electrode of the light-emitting element EL is connected to a wiring supplied with a potential VL. 
     The transistor Tr 3  has a function of controlling current to be supplied to the light-emitting element EL. The capacitor C 2  functions as a storage capacitor. The capacitor C 2  can be omitted when not needed. 
     Note that although the structure in which the anode side of the light-emitting element EL is connected to the transistor Tr 3  is described here, the transistor Tr 3  may be connected to the cathode side. In that case, the values of the potential V H  and the potential VL can be changed as appropriate. 
     In the pixel circuit  400 EL, a large amount of current can flow through the light-emitting element EL when a high potential is supplied to the gate of the transistor Tr 3 , which enables HDR display or the like, for example. In addition, a variation in the electrical characteristics of the transistor Tr 3  and the light-emitting element EL can also be corrected by supply of a correction signal to the wiring S 1  or the wiring S 2 . 
     Note that without limitation to the circuits illustrated in  FIGS.  15 (C) and  15 (D) , a configuration to which a transistor, a capacitor, or the like is further added may be employed. 
     At least part of this embodiment can be implemented in appropriate combination with the other embodiments described in this specification. 
     Embodiment 5 
     In this embodiment, an electronic device of one embodiment of the present invention will be described with reference to drawings. 
     An electronic device illustrated in  FIG.  16    includes a housing and a display panel of one embodiment of the present invention in a display portion. Since the housing can be folded, a small, flexible electronic device provided with a large display region is achieved. 
     The electronic device of one embodiment of the present invention can have a variety of functions. For example, the electronic device can have a function of displaying a variety of information (a still image, a moving image, a text image, and the like) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of executing a variety of software (programs), a wireless communication function, and a function of reading out a program or data stored in a recording medium. 
     An electronic device  200  functions as an input/output device  220 . A sensor  210  and the input/output device  220  include a display portion  230 , an input portion  240 , and a sensing portion  250 . The sensing portion  250  preferably includes an optical sensor. When the electronic device holds the first state, no display can be performed on the display portion  230  with use of a value sensed by the optical sensor. It is possible to reduce the power consumption in a period during which the electronic device is not used by a user. Note that the sensor  210  preferably includes one or more of a position sensor for sensing position information, a camera, a temperature sensor, a fingerprint sensor, and the like. 
     At least part of this embodiment can be implemented in appropriate combination with the other embodiments described in this specification. 
     Embodiment 6 
     Described in this embodiment is the composition of a CAC (Cloud-Aligned Composite)-OS applicable to the OS transistor described in the above embodiments. 
     The CAC-OS has, for example, a composition in which elements included in a metal oxide are unevenly distributed. Materials including unevenly distributed elements each have a size of greater than or equal to 0.5 nm and less than or equal to 10 nm, preferably greater than or equal to 1 nm and less than or equal to 2 nm, or a similar size. Note that in the following description of a metal oxide, a state in which one or more metal elements are unevenly distributed and regions including the metal element(s) are mixed is referred to as a mosaic pattern or a patch-like pattern. The regions each have a size of greater than or equal to 0.5 nm and less than or equal to 10 nm, preferably greater than or equal to 1 nm and less than or equal to 2 nm, or a similar size. 
     Note that a metal oxide preferably contains at least indium. In particular, indium and zinc are preferably contained. In addition, one kind or a plurality of kinds selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like may be contained. 
     For instance, a CAC-OS in an In—Ga—Zn oxide (an In—Ga—Zn oxide in the CAC-OS may be particularly referred to as CAC-IGZO) has a composition in which materials are separated into indium oxide (hereinafter, InO X1  (X1 is a real number greater than 0)) or indium zinc oxide (hereinafter, In X2 Zn Y2 O Z2  (X2, Y2, and Z2 are real numbers greater than 0)) and gallium oxide (hereinafter, GaO X3  (X3 is a real number greater than 0)) or gallium zinc oxide (hereinafter, Ga X4 Zn Y4 O Z4  (X4, Y4, and Z4 are real numbers greater than 0)), for example, so that a mosaic pattern is formed, and mosaic-like InO X1  or In X2 Zn Y2 O Z2  is evenly distributed in the film (which is hereinafter also referred to as cloud-like). 
     That is, the CAC-OS is a composite metal oxide with a composition in which a region including GaO X3  as a main component and a region including In X2 Zn Y2 O Z2  or InO X1  as a main component are mixed. Note that in this specification, for example, when the atomic ratio of In to an element M in a first region is greater than the atomic ratio of In to an element M in a second region, the first region has higher In concentration than the second region. 
     Note that IGZO is a common name, which may specify a compound containing In, Ga, Zn, and O. Typical examples of IGZO include a crystalline compound represented by InGaO 3 (ZnO) m1  (m1 is a natural number) and a crystalline compound represented by In (1+x0) Ga (1-x0) O 3 (ZnO) m0  (−1≤x0≤1; m0 is a given number). 
     The above crystalline compounds have a single crystal structure, a polycrystalline structure, or a CAAC structure. Note that the CAAC structure is a crystal structure in which a plurality of IGZO nanocrystals have c-axis alignment and are connected in the a-b plane direction without alignment. 
     On the other hand, the CAC-OS relates to the material composition of a metal oxide. In a material composition of a CAC-OS including In, Ga, Zn, and O, nanoparticle regions including Ga as a main component are observed in part of the CAC-OS and nanoparticle regions including In as a main component are observed in part thereof. These nanoparticle regions are randomly dispersed to form a mosaic pattern. Therefore, the crystal structure is a secondary element for the CAC-OS. 
     Note that in the CAC-OS, a stacked-layer structure including two or more films with different atomic ratios is not included. For example, a two-layer structure of a film including In as a main component and a film including Ga as a main component is not included. 
     A boundary between the region including GaO X3  as a main component and the region including In X2 Zn Y2 O Z2  or InO X1  as a main component is difficult to clearly observe in some cases. 
     Note that in the case where one kind or a plurality of kinds selected from aluminum, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like are contained instead of gallium, the CAC-OS refers to a composition in which some regions that include the metal element(s) as a main component and are observed as nanoparticles and some regions that include In as a main component and are observed as nanoparticles are randomly dispersed in a mosaic pattern. 
     The CAC-OS can be formed by a sputtering method under conditions where a substrate is not heated, for example. In the case of forming the CAC-OS by a sputtering method, one or more selected from an inert gas (typically, argon), an oxygen gas, and a nitrogen gas may be used as a deposition gas. The ratio of the flow rate of an oxygen gas to the total flow rate of the deposition gas at the time of deposition is preferably as low as possible, and for example, the flow ratio of an oxygen gas is preferably higher than or equal to 0% and lower than 30%, further preferably higher than or equal to 0% and lower than or equal to 10%. 
     The CAC-OS is characterized in that no clear peak is observed in measurement using θ/2θ scan by an Out-of-plane method, which is an X-ray diffraction (XRD) measurement method. That is, it is found from the X-ray diffraction measurement that no alignment in the a-b plane direction and the c-axis direction is observed in the measured region. 
     In an electron diffraction pattern of the CAC-OS that is obtained by irradiation with an electron beam with a probe diameter of 1 nm (also referred to as a nanometer-sized electron beam), a ring-like region with high luminance (a ring region) and a plurality of bright spots in the ring region are observed. Therefore, the electron diffraction pattern indicates that the crystal structure of the CAC-OS includes an nc (nano-crystal) structure with no alignment in the plan-view direction and the cross-sectional direction. 
     Moreover, for example, it can be confirmed by EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) that the CAC-OS in the In—Ga—Zn oxide has a composition in which regions including GaO X3  as a main component and regions including In X2 Zn Y2 O Z2  or InO X1  as a main component are unevenly distributed and mixed. 
     The CAC-OS has a structure different from that of an IGZO compound in which metal elements are evenly distributed, and has characteristics different from those of the IGZO compound. That is, in the CAC-OS, regions including GaO X3  or the like as a main component and regions including In X2 Zn Y2 O Z2  or InO X1  as a main component are phase-separated from each other and form a mosaic pattern. 
     The conductivity of a region including In X2 Zn Y2 O Z2  or InO X1  as a main component is higher than that of a region including GaO X3  or the like as a main component. In other words, when carriers flow through regions including In X2 Zn Y2 O Z2  or InO X1  as a main component, the conductivity of a metal oxide is exhibited. Accordingly, when regions including In X2 Zn Y2 O Z2  or InO X1  as a main component are distributed in a metal oxide like a cloud, high field-effect mobility (μ) can be achieved. 
     By contrast, the insulating property of a region including GaO X3  or the like as a main component is higher than that of a region including In X2 Zn Y2 O Z2  or InO X1  as a main component. In other words, when regions including GaO X3  or the like as a main component are distributed in a metal oxide, leakage current can be suppressed and favorable switching operation can be achieved. 
     Accordingly, when a CAC-OS is used for a semiconductor element, the insulating property derived from GaO X3  or the like and the conductivity derived from In X2 Zn Y2 O Z2  or InO X1  complement each other, whereby a high on-state current (Ion) and high field-effect mobility (μ) can be achieved. 
     A semiconductor element including a CAC-OS has high reliability. Thus, the CAC-OS is suitably used in a variety of semiconductor devices typified by a display. 
     This embodiment can be implemented in appropriate combination with any of the other embodiments. 
     Unless otherwise specified, an on-state current in this specification refers to a drain current of a transistor in an on state. Unless otherwise specified, the on state (sometimes abbreviated as on) refers to a state where the voltage between its gate and source (V G ) is higher than or equal to the threshold voltage (V th ) in an n-channel transistor, and a state where V G  is lower than or equal to V th  in a p-channel transistor. For example, the on-state current of an n-channel transistor refers to a drain current when V G  is higher than or equal to V th . Furthermore, the on-state current of a transistor depends on a voltage between a drain and a source (V D ) in some cases. 
     Unless otherwise specified, an off-state current in this specification refers to a drain current of a transistor in an off state. Unless otherwise specified, the off state (sometimes abbreviated to as off) refers to a state where V G  is lower than V th  in an n-channel transistor, and a state where V G  is higher than V th  in a p-channel transistor. For example, the off-state current of an n-channel transistor refers to a drain current when V G  is lower than V th . The off-state current of a transistor depends on V G  in some cases. Thus, “the off-state current of a transistor is lower than 10 −21  A” may mean that there is V G  at which the off-state current of the transistor is lower than 10 −21  A. 
     Furthermore, the off-state current of a transistor depends on V D  in some cases. Unless otherwise specified, the off-state current in this specification may refer to an off-state current at V D  with an absolute value of 0.1 V, 0.8 V, 1 V, 1.2 V, 1.8 V, 2.5 V, 3 V, 3.3 V, 10 V, 12 V, 16 V, or 20 V. Alternatively, the off-state current may refer to an off-state current at V D  used in a semiconductor device or the like including the transistor. 
     Note that a voltage refers to a potential difference between two points, and a potential refers to electrostatic energy (electric potential energy) of a unit charge at a given point in an electrostatic field. Note that in general, a potential difference between a potential of one point and a reference potential (e.g., a ground potential) is simply called a potential or a voltage, and a potential and a voltage are used as synonymous words in many cases. Therefore, in this specification, a potential may be rephrased as a voltage and a voltage may be rephrased as a potential unless otherwise specified. 
     In this specification and the like, when there is a description which explicitly states that X and Y are connected, the case where X and Y are electrically connected and the case where X and Y are directly connected are regarded as being disclosed in this specification and the like. 
     Here, X and Y each denote an object (e.g., a device, an element, a circuit, a wiring, an electrode, a terminal, a conductive film, or a layer). 
     An example of the case where X and Y are directly connected is the case where X and Y are connected without an element that enables electrical connection between X and Y (e.g., a switch, a transistor, a capacitor, an inductor, a resistor, a diode, a display element, a light-emitting element, or a load). 
     An example of the case where X and Y are electrically connected is the case where at least one element that enables electrical connection between X and Y (e.g., a switch, a transistor, a capacitor, an inductor, a resistor, a diode, a display element, a light-emitting element, or a load) can be connected between X and Y. Note that a switch has a function of controlling whether current flows or not by being in a conduction state (an on state) or a non-conduction state (an off state). Alternatively, the switch has a function of selecting and changing a current path. Note that the case where X and Y are electrically connected includes the case where X and Y are directly connected. 
     REFERENCE NUMERALS 
     C 1 : capacitor, C 2 : capacitor, G 1 : wiring, G 2 : wiring, S 1 : wiring, S 2 : wiring, Tr 1 : transistor, Tr 2 : transistor, Tr 3 : transistor,  10 : electronic device,  10 A: electronic device,  10 B: electronic device,  10 C: electronic device,  11 : display panel,  11   a : display region, lib: display region,  11   c : display region,  11 C: electronic device,  20 : component,  20   a : component,  20   s   1 : opening,  20   s   2 : space,  20   s   3 : opening,  20   s   4 : opening,  21 : component,  21   a : component,  21   b : component,  21   s : space,  22 : component,  22   a : space,  22   b : structure body,  23 : component,  24 : component,  25 : component,  25   a : component,  25   b : component,  25   c : component,  25   d : component,  26 : movable portion,  27 : housing,  30 : movable module,  30   a : component,  30   b : movable portion,  31   a : component,  31   b : movable portion,  32   a : component,  32   b : movable portion,  32   c : space,  33   a : component,  33   b : movable portion,  33   c : space,  34   a : component,  34   b : component,  40 : fixing unit,  50 : electronic component,  51 : electronic component,  52 : electronic component,  53 : electronic component,  60 : space,  200 : electronic device,  210 : sensor,  220 : input/output device,  230 : display portion,  240 : input portion,  250 : sensing portion,  400 : pixel circuit,  400 EL: pixel circuit,  400 LC: pixel circuit,  401 : circuit,  401 EL: circuit,  401 LC: circuit,  501 : pixel circuit,  504 : driver circuit portion,  550 : transistor,  552 : transistor,  554 : transistor,  560 : capacitor,  562 : capacitor,  570 : liquid crystal element,  572 : light-emitting element,  700 : display panel,  701 : substrate,  702 : pixel portion,  704 : source driver,  705 : substrate,  706 : gate driver,  707 : terminal portion,  708 : terminal portion,  710 : signal line,  711 : wiring portion,  712 : sealant,  716 : FPC,  730 : insulating film,  732 : sealing film,  734 : insulating film,  736 : coloring film,  738 : light-blocking film,  750 : transistor,  752 : transistor,  760 : connection electrode,  770 : planarization insulating film,  772 : conductive layer,  773 : insulating layer,  774 : conductive layer,  775 : liquid crystal element,  776 : liquid crystal layer,  780 : anisotropic conductive film,  782 : light-emitting element,  786 : EL layer,  788 : conductive film,  790 : capacitor,  791 : protection circuit