Patent Publication Number: US-10312255-B2

Title: Semiconductor device and method for manufacturing same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a division of application Ser. No. 15/071,006, filed Mar. 15, 2016 and is based upon and claims the benefit of priority from U.S. Provisional Application 62/237,723, filed Oct. 6, 2015; the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a semiconductor device and a method for manufacturing the same. 
     BACKGROUND 
     For example, a method for manufacturing a three-dimensional semiconductor memory device includes processes of forming a stacked body including a plurality of electrode layers on a substrate, making a hole in the stacked body to extend in the stacking direction, and forming a film on a side surface of the hole. The film that is formed on the side surface of the hole is continuous in the stacking direction; and it is difficult to divide such a film in the stacking direction by anisotropic etching through the hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A to 8  are schematic cross-sectional views showing a method for manufacturing a semiconductor device of a first embodiment; 
         FIGS. 9A to 9C  are schematic plan views showing a method for manufacturing the semiconductor device of the first embodiment; 
         FIG. 10  is a schematic perspective view of a memory cell array of a semiconductor device of a second embodiment; 
         FIG. 11  is a schematic cross-sectional view of the memory cell array of the semiconductor device of the second embodiment; 
         FIG. 12  is an enlarged schematic cross-sectional view of some of the memory cell array shown in  FIG. 11 ; 
         FIGS. 13 to 33B  are schematic cross-sectional views showing a method for manufacturing the semiconductor device of the second embodiment; 
         FIGS. 34A to 38B  are schematic cross-sectional views showing a method for manufacturing a semiconductor device of reference example; and 
         FIGS. 39A to 45  are schematic cross-sectional views showing a method for manufacturing a semiconductor device of a third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a semiconductor device includes a substrate, a stacked body, a semiconductor film, a plurality of charge storage films, and a plurality of insulating films. The stacked body is provided above the substrate. The stacked body includes a plurality of electrode layers stacked with a first air gap interposed. The semiconductor film extends in a stacking direction through the stacked body. The plurality of charge storage films are provided between the semiconductor film and the electrode layers. The plurality of charge storage films are separated in the stacking direction with a second air gap interposed. The plurality of insulating films are provided on side surfaces of the electrode layers opposing the charge storage films, on portions of surfaces of the electrode layers continuous from the side surfaces and opposing the first air gap, and on corners of the electrode layers between the portions and the side surfaces. The plurality of insulating films are divided in the stacking direction with a third air gap interposed and without the charge storage films being interposed. The third air gap communicates with the first air gap and the second air gap between the first air gap and the second air gap. 
     Embodiments will now be described with reference to the drawings. The same components are marked with the same reference numerals in the drawings. 
     First, a method for manufacturing a semiconductor device of a first embodiment will be described with reference to  FIG. 1A  to  FIG. 9C . 
       FIG. 1A  to  FIG. 8  are schematic cross-sectional views showing the method for manufacturing the semiconductor device of the first embodiment. 
       FIG. 9A  to  FIG. 9C  are schematic plan views showing the method for manufacturing the semiconductor device of the first embodiment. 
     The method for manufacturing the semiconductor device of the first embodiment includes a process of working a stacked body  200  shown in  FIG. 1A . The stacked body  200  includes a first layer  171 , a second layer  172 , and a sacrificial layer  173  provided between the first layer  171  and the second layer  172 . 
     For example, the first layer  171  is formed on a not-shown substrate or other layer. The sacrificial layer  173  is formed on the first layer  171 ; and the second layer  172  is formed on the sacrificial layer  173 . The sacrificial layer  173  is interposed between the first layer  171  and the second layer  172 . 
     The sacrificial layer  173  is a layer of a different type of material from the first layer  171  and the second layer  172 ; and the etching selectivity of the sacrificial layer  173  with respect to the first layer  171  and the second layer  172  is sufficiently high. The first layer  171  and the second layer  172  may be of the same type of material or of different types of materials. 
     A first through-portion  151  is made in the stacked body  200  as shown in  FIG. 1B . The first through-portion  151  is, for example, a hole or a slit made by anisotropic etching such as reactive ion etching (RIE). The first through-portion  151  pierces the second layer  172 , the sacrificial layer  173  and the first layer  171 , and extends in the stacking direction of the second layer  172 , the sacrificial layer  173  and the first layer  171 . 
     The surface of the first layer  171  along the first through-portion  151 , the surface of the second layer  172  along the first through-portion  151 , and the surface of the sacrificial layer  173  along the first through-portion  151  are exposed in the first through-portion  151 . 
     Then, the sacrificial layer  173  is etched using an etchant or an etching gas supplied to the first through-portion  151 . For example, the sacrificial layer  173  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the first through-portion  151 . The first layer  171  and the second layer  172  are, for example, metal films that have etching resistance to the etchant containing hydrofluoric acid. 
     The etching of the sacrificial layer  173  progresses from the end surface of the sacrificial layer  173  exposed in the first through-portion  151 ; and the end surface of the sacrificial layer  173  recedes in the diametral direction or width direction of the first through-portion  151  to be separated from the first through-portion  151  as shown in  FIG. 1C . 
     By the etching of the sacrificial layer  173 , an air gap  153  that communicates with the first through-portion  151  is made between the first layer  171  and the second layer  172 . One portion of the sacrificial layer  173  remains between the first layer  171  and the second layer  172 . The air gap  153  is made between the first through-portion  151  and the remaining one portion of the sacrificial layer  173 . 
     Then, a first film  133  shown in  FIG. 2A  is formed in the air gap  153  by chemical vapor deposition (CVD) or atomic layer deposition (ALD). The source gas in the film formation is supplied to the air gap  153  through the first through-portion  151 . The first film  133  is formed also on the side surface of the second layer  172  adjacent to the first through-portion  151  and the side surface of the first layer  171  adjacent to the first through-portion  151 . 
     The first film  133  is formed conformally along the side surface of the second layer  172 , the lower surface of the second layer  172  adjacent to the air gap  153  (the surface opposing the first layer  171 ), the side surface of the sacrificial layer  173  adjacent to the air gap  153 , the upper surface of the first layer  171  adjacent to the air gap  153  (the surface opposing the second layer  172 ), and the side surface of the first layer  171 . 
     The film thickness of the first film  133  is thinner than ½ of the height (the length in the stacking direction) of the air gap  153 . Therefore, one portion  153   a  of the air gap  153  remains between the first film  133  formed on the lower surface of the second layer  172  and the first film  133  formed on the upper surface of the first layer  171 . 
     The remaining air gap  153   a  communicates with the first through-portion  151  and extends from the first through-portion  151  toward the sacrificial layer  173 . 
     The first film  133  is a film of a different type of material from the first layer  171  and the second layer  172 ; and the etching selectivity of the first film  133  with respect to the first layer  171  and the second layer  172  is sufficiently high. 
     Then, a second film  132  shown in  FIG. 2B  is formed in the air gap  153   a  and on the side surface of the first film  133  adjacent to the first through-portion  151 . The second film  132  includes a first portion  132   a  filled into the air gap  153   a , and a second portion  132   b  provided on the side surface of the first film  133  and extending in the stacking direction of the stacked body  200 . 
     The first portion  132   a  is provided as one body with the second portion  132   b  and extends from the second portion  132   b  toward the sacrificial layer  173 . The first portion  132   a  is provided between the first film  133  formed on the lower surface of the second layer  172  and the first film  133  formed on the upper surface of the first layer  171 . 
     The second film  132  is a film of a different type of material from the first layer  171 , the second layer  172 , and the first film  133 ; and the etching selectivity of the second film  132  with respect to the first layer  171 , the second layer  172 , and the first film  133  is sufficiently high. 
     A third film  131  is formed on the side surface of the second portion  132   b  of the second film  132  adjacent to the first through-portion  151 . The third film  131  extends continuously in the stacking direction of the stacked body  200 . The third film  131  is a film of a different type of material from the second film  132 ; and the etching selectivity of the second film  132  with respect to the third film  131  is sufficiently high. 
     The first through-portion  151  may be filled with the first film  133 , the second film  132 , and the third film  131 ; or one portion of the first through-portion  151  may remain at the side of the third film  131  as a cavity. Or, another film may be formed on the side surface of the third film  131 . 
     Then, as shown in  FIG. 3A , a second through-portion  152  is made in the region of the stacked body  200  where the sacrificial layer  173  remains. The second through-portion  152  is, for example, a hole or a slit made by anisotropic etching such as RIE. The second through-portion  152  pierces the second layer  172 , the sacrificial layer  173  and the first layer  171 , and extends in the stacking direction of the second layer  172 , the sacrificial layer  173  and the first layer  171 . 
     The surface of the first layer  171  along the second through-portion  152 , the surface of the second layer  172  along the second through-portion  152 , and the surface of the sacrificial layer  173  along the second through-portion  152  are exposed in the second through-portion  152 . 
     Then, the sacrificial layer  173  that remains between the first layer  171  and the second layer  172  is etched using an etchant or an etching gas supplied to the second through-portion  152 . For example, the sacrificial layer  173  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the second through-portion  152 . 
     By the etching of the sacrificial layer  173 , an air gap  154  that communicates with the second through-portion  152  is made between the first layer  171  and the second layer  172  as shown in  FIG. 3B . An end portion  133   a  of the first film  133  is exposed in the air gap  154 . 
     Or, the first film  133  can be exposed at the side surface of the second through-portion  152  by making the second through-portion  152  so that the second through-portion  152  and the end portion  133   a  of the first film  133  overlap. 
     Then, the end portion  133   a  of the first film  133  that is directly exposed in the second through-portion  152  or exposed in the second through-portion  152  via the air gap  154  is etched. The etching of the first film  133  is caused to progress from the end portion  133   a ; and the first portion  132   a  of the second film  132  is exposed as shown in  FIG. 4A . 
     For example, the first film  133  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the second through-portion  152 . For example, the second film  132  which is a silicon nitride film has etching resistance to the etchant containing hydrofluoric acid. 
     The first layer  171  includes a corner  171   a  between the side surface on the first through-portion  151  side and the surface opposing the second layer  172 . The side surface of the first layer  171  is continuous from the surface opposing the second layer  172  with the corner  171   a  interposed. The second layer  172  includes a corner  172   a  between the side surface on the first through-portion  151  side and the surface opposing the first layer  171 . The side surface of the second layer  172  is continuous from the surface opposing the first layer  171  with the corner  172   a  interposed. 
     The first film  133  includes a corner  133   b  that covers the corner  171   a  formed along the corner  171   a  of the first layer  171 , and a corner  133   b  that covers the corner  172   a  formed along the corner  172   a  of the second layer  172 . The base on the second portion  132   b  side of the first portion  132   a  of the second film  132  is interposed between the corners  133   b  in the stacking direction of the stacked body  200 . The first portion  132   a  and the second portion  132   b  of the second film  132  are continuous along the corners  133   b  of the first films  133  and cover the corners  133   b.    
     The etching of the first film  133  is stopped at a timing when one portion on the tip side of the first portion  132   a  of the second film  132  is exposed. The corners  133   b  of the first films  133  remain at this point in time. 
     Then, etching of the second film  132  is caused to progress from the exposed first portion  132   a . For example, the second film  132  which is a silicon nitride film is etched by supplying an etchant containing phosphoric acid to the second through-portion  152 . The first film  133  which is a silicon oxide film and the first layer  171  and the second layer  172  which are metal films have etching resistance to the etchant containing phosphoric acid. 
     The first portion  132   a  of the second film  132  is etched and removed; and an air gap  155  is made between the first film  133  formed on the upper surface of the first layer  171  and the first film  133  formed on the lower surface of the second layer  172  as shown in  FIG. 4B . 
     After the first portion  132   a  is removed, the etching of the second film  132  is caused to progress further; and the second portion  132   b  that is formed on the side surfaces of the first films  133  is divided in the stacking direction. At this time, the third film  131  functions as an etching stopper; and the etchant does not flow around to the back surface (the surface on the side opposite to the interfaces with the first films  133 ) side of the second portion  132   b.    
     An air gap  156  is made in the second portion  132   b  of the second film  132  that was continuous in the stacking direction of the stacked body  200 ; and the second portion  132   b  is divided in the stacking direction of the stacked body  200  with the air gap  156  interposed. 
     Here,  FIG. 34A  and  FIG. 34B  are schematic cross-sectional views showing a reference example of a method for dividing, in the vertical direction, a film formed along the stacking direction (the vertical direction) of a stacked body. 
     The film  132  in  FIG. 34A  is a film to be etched (to be divided);  FIG. 34A  is prior to the etching of the film  132 ; and  FIG. 34B  is after the etching of the film  132 . The film  131  that functions as an etching stopper is formed on the side surface of the film  132 . 
     The film  132  that is formed on the side surface of the first through-portion  151  is etched by an etchant supplied through the second through-portion  152  and the air gap  154  made between the first layer  171  and the second layer  172 . 
     The film  132  is etched isotropically from the surface exposed in the air gap  154  by the etchant entering from the air gap  154 . Also, the film  132  recedes in the vertical direction along the side surface of the first layer  171  due to isotropic etching having the corner  171   a  of the first layer  171  as a start point. Similarly, the film  132  also recedes in the vertical direction along the side surface of the second layer  172  due to isotropic etching having the corner  172   a  of the second layer  172  as a start point. 
     To divide the film  132  in the vertical direction, it is necessary for the etching of the film  132  to progress the amount of the film thickness of the film  132  from the surface exposed in the air gap  154 . In the case where the film thickness of the film  132  is thick, the receded amount in the vertical direction increases by this amount; and there is a concern that the amount of the film  132  remaining on the side surface of the first layer  171  and the film  132  remaining on the side surface of the second layer  172  may be little. 
     In the case where the thickness of the first layer  171  and the thickness of the second layer  172  are thinner than the film thickness of the film  132 , there may be cases where the film  132  does not remain on the side surface of the first layer  171  and the side surface of the second layer  172 . 
     Conversely, according to the first embodiment described above, the first film  133  is interposed between the second film  132  to be divided and the first layer  171 , and between the second film  132  and the second layer  172 . 
     As shown in  FIG. 4A , the corner  133   b  of the first film  133  covering the corner  171   a  of the first layer  171  is separated from the corner  171   a  of the first layer  171  by an amount corresponding to the film thickness of the first film  133 . Similarly, the corner  133   b  of the first film  133  covering the corner  172   a  of the second layer  172  is separated from the corner  172   a  of the second layer  172  by an amount corresponding to the film thickness of the first film  133 . 
     After the first portion  132   a  of the second film  132  interposed between the first films  133  disappears, etching of the second portion  132   b  progresses isotropically from the corners  133   b  of the first films  133  as start points; and the second portion  132   b  is divided in the stacking direction (the vertical direction) of the stacked body  200 . 
     In the reference example shown in  FIG. 34A  and  FIG. 34B , the etching start point of the film  132  is proximal to the side surface of the first layer  171  and the side surface of the second layer  172 . Conversely, according to the first embodiment, the etching start point of the second portion  132   b  of the second film  132  is separated from the corner  171   a  of the first layer  171  and the corner  172   a  of the second layer  172 . The etching start point of the second portion  132   b  is not proximal to the side surface of the first layer  171  and the side surface of the second layer  172 . 
     There are distances from the etching start point of the second portion  132   b  to the portion of the second portion  132   b  opposing the side surface of the first layer  171 , and from the etching start point of the second portion  132   b  to the portion of the second portion  132   b  opposing the side surface of the second layer  172 . It is desirable for the distances to be not less than the film thickness of the second portion  132   b.    
     Therefore, the second portion  132   b  can be divided in the vertical direction before the etching progresses to the portion of the second portion  132   b  opposing the side surface of the first layer  171  and the portion of the second portion  132   b  opposing the side surface of the second layer  172 . Or, the consumed amounts can be suppressed for the portion of the second portion  132   b  opposing the side surface of the first layer  171  and the portion of the second portion  132   b  opposing the side surface of the second layer  172  until the dividing of the second portion  132   b  in the vertical direction ends. The second film  132  can be divided in the vertical direction while causing a sufficient amount of the second film  132  to remain at the portion opposing the side surface of the first layer  171  and the portion opposing the side surface of the second layer  172 . 
     The first film  133  also is divided in the stacking direction (the vertical direction) of the stacked body  200  as shown in  FIG. 4A  by the etching of the end portion  133   a  of the first film  133  covering the tip portion of the first portion  132   a  of the second film  132  in  FIG. 3B . Further, the air gap  155  is made between the first films  133  adjacent to each other in the vertical direction by the disappearance of the first portion  132   a.    
     Even after the etching to divide the second portion  132   b  of the second film  132  has ended, the corners  133   b  of the first films  133  and the portions extending along the side surface of the first layer  171  and the side surface of the second layer  172  from the corners  133   b  remain as shown in  FIG. 4B . The corners  133   b  of the first films  133  are adjacent to the region (the air gap  156 ) between the multiple second portions  132   b  that are divided. 
     Accordingly, the etching of the second portion  132   b  of the second film  132  can be prevented from progressing from portions other than the portions proximal to the corners  133   b  of the first films  133 . After the second portion  132   b  of the second film  132  is divided in the vertical direction, the portions extending along the side surface of the first layer  171  and the side surface of the second layer  172  from the corners  133   b  of the first films  133  may be removed by etching. 
     The length in the vertical direction of the air gap  156  between the second portions  132   b  of the second film  132  is longer than the length in the vertical direction of the air gap  155  between the first films  133 . The spacing between the second portions  132   b  of the second film  132  divided in the vertical direction with the air gap  156  interposed is larger than the spacing between the first films  133  divided in the vertical direction with the air gap  155  interposed. 
     According to the first embodiment described above, each of different types of stacked films (the first film  133  and the second film  132 ) stacked on the side surface of the first through-portion  151  which is a hole or a slit made in the stacked body  200  can be divided in the stacking direction. 
     For example, in the case where the first layer  171 , the second layer  172 , and the first film  133  are conductive, shorts between the first layer  171  and the second layer  172  via the first film  133  can be prevented by dividing the first film  133  in the vertical direction. Or, for example, in the case where the first film  133  or the second film  132  includes a charge storage film, the movement in the vertical direction of the stored charge can be prevented. 
     The first through-portion  151  is, for example, the hole shown in  FIG. 9A . For example,  FIG. 2B  described above corresponds to an A-A cross section of  FIG. 9A . The third film  131  is formed on the innermost side proximal to the central axis of the hole  151 . The third film  131  is continuous in the circumferential direction of the hole  151 . The second portion  132   b  of the second film  132  is formed to continuously surround the third film  131  from the outer circumferential side. The first film  133  is formed to continuously surround the second portion  132   b  from the outer circumferential side. 
     The edge of the end portion  133   a  of the first film  133  adjacent to the sacrificial layer  173  between the first layer  171  and the second layer  172  is illustrated by a broken line in  FIG. 9A . Also, the tip of the first portion  132   a  of the second film  132  is illustrated by a broken line in  FIG. 9A . 
     Or, the first through-portion  151  is, for example, the slit shown in  FIG. 9B . For example,  FIG. 2B  corresponds to an A-A cross section of  FIG. 9B . The third film  131  is formed on the innermost side proximal to the center of the slit  151 . The third film  131  is continuous along the contour of the slit  151 . The second portion  132   b  of the second film  132  is formed to continuously surround the third film  131  from the outer side. The first film  133  is formed to continuously surround the second portion  132   b  from the outer side. 
     The edge of the end portion  133   a  of the first film  133  adjacent to the sacrificial layer  173  between the first layer  171  and the second layer  172  is illustrated by a broken line in  FIG. 9B . Also, the tip of the first portion  132   a  of the second film  132  is illustrated by a broken line in  FIG. 9B . 
     Or, the first through-portion  151  is, for example, the slit shown in  FIG. 9C . For example,  FIG. 2B  corresponds to an A-A cross section of  FIG. 9C . The first film  133  is formed along the slit  151  on the side surface of the first layer  171  and the side surface of the second layer  172 ; the second portion  132   b  of the second film  132  is formed along the slit  151  on the side surface of the first film  133 ; and the third film  131  is formed along the slit  151  on the side surface of the second portion  132   b.    
     The edge of the end portion  133   a  of the first film  133  adjacent to the sacrificial layer  173  between the first layer  171  and the second layer  172  is illustrated by a broken line in  FIG. 9C . Also, the tip of the first portion  132   a  of the second film  132  is illustrated by a broken line in  FIG. 9C . 
     Another example of the method for manufacturing the semiconductor device of the first embodiment will now be described. 
       FIG. 5A  to  FIG. 8  are schematic cross-sectional views showing another example of the manufacturing method. 
     In  FIG. 5A  to  FIG. 8 , the same components as the components shown in  FIG. 1A  to  FIG. 4B  described above are marked with the same reference numerals, and a detailed description thereof is omitted. 
     After making the first through-portion  151  in the stacked body  200 , the sacrificial layer  173  is etched using an etchant or an etching gas supplied to the first through-portion  151 . For example, the sacrificial layer  173  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the first through-portion  151 . 
     The etching of the sacrificial layer  173  progresses from the end surface of the sacrificial layer  173  exposed in the first through-portion  151 ; and the end surface of the sacrificial layer  173  recedes in the diametral direction or width direction of the first through-portion  151  so that the end surface of the sacrificial layer  173  separates from the first through-portion  151  as shown in  FIG. 5A . 
     The air gap  153  that communicates with the first through-portion  151  is made between the first layer  171  and the second layer  172  by the etching of the sacrificial layer  173 . One portion of the sacrificial layer  173  remains between the first layer  171  and the second layer  172 . 
     Then, the first film  133  shown in  FIG. 5B  is formed in the air gap  153  by CVD or ALD. The first film  133  is formed also on the side surface of the second layer  172  adjacent to the first through-portion  151  and the side surface of the first layer  171  adjacent to the first through-portion  151 . 
     The first film  133  is formed conformally along the side surface of the second layer  172 , the lower surface of the second layer  172  adjacent to the air gap  153  (the surface opposing the first layer  171 ), the side surface of the sacrificial layer  173  adjacent to the air gap  153 , the upper surface of the first layer  171  adjacent to the air gap  153  (the surface opposing the second layer  172 ), and the side surface of the first layer  171 . 
     In the example shown in  FIG. 5A , the receded amount of the sacrificial layer  173  from the first through-portion  151  is less than that of the example shown in  FIG. 1C  described above; and the air gap  153  is filled with the first film  133 . However, the film thickness of the first film  133  is thinner than ½ of the height (the length in the stacking direction) of the air gap  153 . Therefore, a stepped portion that reflects the stepped portion between the air gap  153  and the side surface of the first layer  171 , and the stepped portion between the air gap  153  and the side surface of the second layer  172  is formed in the side surface of the first film  133  on the first through-portion  151  side. In other words, an air gap  253  that extends from the first through-portion  151  toward the sacrificial layer  173  is made in the side surface of the first film  133  on the first through-portion  151  side. 
     Then, the second film  132  shown in  FIG. 6A  is formed in the air gap  253  and on the side surface of the first film  133  adjacent to the first through-portion  151 . The second film  132  includes the first portion  132   a  that is filled into the air gap  253 , and the second portion  132   b  that is provided on the side surface of the first film  133  and extends in the stacking direction of the stacked body  200 . 
     The first portion  132   a  is provided as one body with the second portion  132   b  and extends in a protruding configuration from the second portion  132   b  toward the sacrificial layer  173 . 
     The third film  131  is formed on the side surface of the second portion  132   b  of the second film  132  adjacent to the first through-portion  151 . The first through-portion  151  may be filled with the first film  133 , the second film  132 , and the third film  131 ; or one portion of the first through-portion  151  may remain as a cavity at the side of the third film  131 . Or, another film may be formed on the side surface of the third film  131 . 
     Then, the second through-portion  152  is made as shown in  FIG. 6B  in the region of the stacked body  200  where the sacrificial layer  173  remains. The surface of the first layer  171  along the second through-portion  152 , the surface of the second layer  172  along the second through-portion  152 , and the surface of the sacrificial layer  173  along the second through-portion  152  are exposed in the second through-portion  152 . 
     Then, the sacrificial layer  173  that remains between the first layer  171  and the second layer  172  is etched using an etchant or an etching gas supplied to the second through-portion  152 . For example, the sacrificial layer  173  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the second through-portion  152 . 
     The air gap  154  that communicates with the second through-portion  152  is made between the first layer  171  and the second layer  172  as shown in  FIG. 7A  by the etching of the sacrificial layer  173 . The end portion  133   a  of the first film  133  is exposed in the air gap  154 . 
     Then, the end portion  133   a  of the first film  133  exposed in the second through-portion  152  through the air gap  154  is etched. The etching of the first film  133  is caused to progress from the end portion  133   a ; and the first portion  132   a  of the second film  132  is exposed as shown in  FIG. 7B . 
     For example, the first film  133  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the second through-portion  152 . For example, the second film  132  which is a silicon nitride film has etching resistance to the etchant containing hydrofluoric acid. 
     The etching of the first film  133  is stopped at a timing when one portion on the tip side of the first portion  132   a  of the second film  132  is exposed. The corners  133   b  of the first films  133  remain; and the base on the second portion  132   b  side of the first portion  132   a  of the second film  132  is interposed between the corners  133   b  in the stacking direction of the stacked body  200  as shown in  FIG. 7B . At this point in time, the side surface of the second portion  132   b  of the second film  132  on the first film  133  side is covered with the first film  133 . 
     Then, etching of the second film  132  is caused to progress from the exposed first portion  132   a . For example, the second film  132  which is a silicon nitride film is etched by supplying an etchant containing phosphoric acid to the second through-portion  152 . The first film  133  which is a silicon oxide film, and the first and second layers  171 ,  172  which are metal films have etching resistance to the etchant containing phosphoric acid. 
     As shown in  FIG. 8 , the first portion  132   a  of the second film  132  is etched and removed. After the first portion  132   a  is removed, the etching of the second film  132  is caused to progress further; and the second portion  132   b  formed on the side surfaces of the first films  133  is divided in the stacking direction. At this time, the third film  131  functions as an etching stopper; and the etchant does not flow around to the back surface (the surface on the side opposite to the interfaces with the first films  133 ) side of the second portion  132   b.    
     The air gap  156  is made in the second portion  132   b  of the second film  132  that was continuous in the stacking direction of the stacked body  200 ; and the second portion  132   b  is divided in the stacking direction of the stacked body  200  with the air gap  156  interposed. 
     In the example shown in  FIG. 5A  to  FIG. 8  as well, the first film  133  is interposed between the second film  132  to be divided and the first layer  171 , and between the second film  132  and the second layer  172 . 
     As shown in  FIG. 7A , the corner  133   b  of the first film  133  covering the corner  171   a  of the first layer  171  is separated from the corner  171   a  of the first layer  171  by an amount corresponding to the film thickness of the first film  133 . Similarly, the corner  133   b  of the first film  133  covering the corner  172   a  of the second layer  172  is separated from the corner  172   a  of the second layer  172  by an amount corresponding to the film thickness of the first film  133 . 
     After the first portion  132   a  of the second film  132  interposed between the first films  133  disappears, etching of the second portion  132   b  progresses isotropically from the corners  133   b  of the first films  133  as start points; and the second portion  132   b  is divided in the stacking direction (the vertical direction) of the stacked body  200 . 
     The etching start point of the second portion  132   b  of the second film  132  is separated from the corner  171   a  of the first layer  171  and the corner  172   a  of the second layer  172  and is not proximal to the side surface of the first layer  171  and the side surface of the second layer  172 . There are distances from the etching start point of the second portion  132   b  to the portion of the second portion  132   b  opposing the side surface of the first layer  171 , and from the etching start point of the second portion  132   b  to the portion of the second portion  132   b  opposing the side surface of the second layer  172 . It is desirable for the distances to be not less than the film thickness of the second portion  132   b.    
     Therefore, the second portion  132   b  can be divided in the vertical direction before the etching progresses to the portion of the second portion  132   b  opposing the side surface of the first layer  171  and the portion of the second portion  132   b  opposing the side surface of the second layer  172 . Or, the consumed amounts can be suppressed for the portion of the second portion  132   b  opposing the side surface of the first layer  171  and the portion of the second portion  132   b  opposing the side surface of the second layer  172  until the dividing of the second portion  132   b  in the vertical direction ends. The second film  132  can be divided in the vertical direction while causing a sufficient amount of the second film  132  to remain at the portion of opposing the side surface of the first layer  171  and the portion opposing the side surface of the second layer  172 . 
     The first film  133  also is divided in the stacking direction (the vertical direction) of the stacked body  200  as shown in  FIG. 7B  by the end portion  133   a  of the first film  133  shown in  FIG. 7A  being etched. 
     In the method shown in  FIG. 5A  to  FIG. 8  as well, each of different types of stacked films (the first film  133  and the second film  132 ) stacked on the side surface of the first through-portion  151  which is a hole or a slit made in the stacked body  200  can be divided in the stacking direction. 
     Even after the etching to divide the second portion  132   b  of the second film  132  has ended, the corners  133   b  of the first films  133  and the portions extending along the side surface of the first layer  171  and the side surface of the second layer  172  from the corners  133   b  remain as shown in  FIG. 8 . Accordingly, the etching of the second portion  132   b  of the second film  132  can be prevented from progressing from portions other than the portions proximal to the corners  133   b  of the first films  133 . 
     One portion of the first film  133  protrudes in the vertical direction to be adjacent to the region (the air gap  156 ) between the multiple second portions  132   b  that are divided. The corner  133   b  of the first film  133  remains at the tip of the protruding portion. The portion of the first film  133  protruding in the vertical direction may be removed by etching after dividing the second portion  132   b  of the second film  132  in the vertical direction. 
     A second embodiment will now be described. 
     In the second embodiment, a semiconductor memory device that includes, for example, a memory cell array having a three-dimensional structure will be described as the semiconductor device. 
       FIG. 10  is a schematic perspective view of a memory cell array  1  of the semiconductor device of the second embodiment. 
     In  FIG. 10 , two mutually-orthogonal directions parallel to a major surface of a substrate  10  are taken as an X-direction and a Y-direction; and a direction orthogonal to both the X-direction and the Y-direction is taken as a Z-direction (a stacking direction). 
     As shown in  FIG. 10 , the memory cell array  1  includes the substrate  10 , a stacked body  100  provided above the substrate  10 , a plurality of columnar units CL, a plurality of interconnect units LI, and upper layer interconnects provided above the stacked body  100 . In  FIG. 10 , for example, bit lines BL and a source line SL are shown as the upper layer interconnects. 
     The interconnect unit LI is provided between the substrate  10  and the upper layer interconnect, and spreads in a plate configuration in the Z-direction and the X-direction. The interconnect unit LI divides the stacked body  100  into multiple blocks in the Y-direction. 
     The columnar units CL are formed in a circular columnar or an elliptical columnar configuration extending in the Z-direction through the stacked body  100 . For example, the plurality of columnar units CL have a staggered arrangement. Or, the plurality of columnar units CL may have a square lattice arrangement along the X-direction and the Y-direction. 
     The multiple bit lines BL are separated from each other in the X-direction; and each of the bit lines BL extends in the Y-direction. 
     The upper ends of semiconductor films  20  of the columnar units CL described below are connected to the bit lines BL via contact Cb. The plurality of columnar units CL, each of which is selected from each of blocks separated in the Y-direction by the interconnect unit LI, are connected to one common bit line BL. 
       FIG. 11  is a schematic cross-sectional view of the substrate  10 , the stacked body  100 , the columnar units CL, and the interconnect units LI. The Y-direction and the Z-direction shown in  FIG. 11  correspond to the Y-direction and the Z-direction shown in  FIG. 10 . Insulating films  42 ,  43 , and  63  shown in  FIG. 11  are not shown in  FIG. 10 . 
     The stacked body  100  includes a plurality of electrode layers  70  stacked on the substrate  10  via an insulating film  41 . The plurality of electrode layers  70  are stacked, with the air gap  40   a  interposed, at a prescribed period in a direction (the Z-direction) perpendicular to the major surface of the substrate  10 . The electrode layer  70  contains a metal or a metal silicide. 
     The air gap  40   a  is made between the electrode layer  70  and the electrode layer  70  adjacent to each other in the stacking direction. The insulating film  41  is provided between the substrate  10  and the electrode layer  70  of the lowermost layer. The insulating film  42  is provided on the electrode layer  70  of the uppermost layer; and the insulating film  43  is provided on the insulating film  42 . 
       FIG. 12  is an enlarged cross-sectional view of some of the components shown in  FIG. 11 . 
     The columnar unit CL is a stacked film including a memory film  30 , the semiconductor film  20 , and a core film  50  that is insulative. The semiconductor film  20  extends in a pipe-like configuration through the stacked body  100  in the stacking direction (the Z-direction). The core film  50  is provided on the inner side of the semiconductor film  20  having the pipe-like configuration. 
     The upper end of the semiconductor film  20  is connected to the bit line BL via the contact Cb shown in  FIG. 10 . The lower end of the semiconductor film  20  is connected to the substrate  10  as shown in  FIG. 11 . 
     The memory film  30  includes a tunneling insulating film  31 , a charge storage film  32 , and a blocking insulating film  33 . The blocking insulating film  33 , the charge storage film  32 , and the tunneling insulating film  31  are provided between the electrode layer  70  and the semiconductor film  20  in order from the electrode layer  70  side. The tunneling insulating film  31  contacts the semiconductor film  20 . The blocking insulating film  33  contacts the electrode layer  70 . The charge storage film  32  is provided between the blocking insulating film  33  and the tunneling insulating film  31 . 
     The tunneling insulating film  31  and the semiconductor film  20  extend to be continuous in the stacking direction of the stacked body  100 . The charge storage film  32  is divided in the stacking direction with an air gap  40   b  interposed. An air gap  40   c  that communicates with the air gap  40   a  and the air gap  40   b  is made between the air gap  40   a  between the electrode layers  70  and the air gap  40   b  between the charge storage films  32 ; and the blocking insulating film  33  is divided in the stacking direction with the air gap  40   c  interposed. The charge storage film  32  is not interposed between the blocking insulating films  33  separated above and below. 
     The length in the stacking direction of the air gap  40   b  is longer than the length in the stacking direction of the air gap  40   c . In other words, the spacing between the multiple charge storage films  32  separated from each other in the stacking direction with the air gap  40   b  interposed is larger than the spacing between the multiple blocking insulating films  33  separated from each other in the stacking direction with the air gap  40   c  interposed. 
     The length in the stacking direction of the air gap  40   a  is longer than the length in the stacking direction of the air gap  40   c . In other words, the spacing between the multiple electrode layers  70  separated from each other in the stacking direction with the air gap  40   a  interposed is larger than the spacing between the multiple blocking insulating films  33  separated from each other in the stacking direction with the air gap  40   c  interposed. 
     The charge storage film  32  is provided between the blocking insulating film  33  and the semiconductor film  20  and surrounds the semiconductor film  20  from the outer circumferential side. 
     The side surface of the semiconductor film  20  opposing the charge storage film  32  and the side surface of the semiconductor film  20  opposing the air gap  40   b  are continuous along the stacking direction. 
     The charge storage film  32 , the tunneling insulating film  31 , and the semiconductor film  20  do not enter between the electrode layers  70  adjacent to each other in the stacking direction. 
     The electrode layer  70  has a side surface  70   b  opposing the charge storage film  32 , a surface  70   c  opposing the air gaps  40   a  and  40   c  and formed to be continuous from the side surface  70   b , and a corner  70   a  between the side surface  70   b  and the surface  70   c.    
     The blocking insulating film  33  is provided on the corner  70   a , the side surface  70   b , and one portion of the surface  70   c  of the electrode layer  70 , and covers the corner  70   a , the side surface  70   b , and the one portion of the surface  70   c  of the electrode layer  70 . The blocking insulating film  33  is not formed on the entire surface  70   c  of the electrode layer  70 . Only one portion of the surface  70   c  of the electrode layer  70  in the vicinity of the corner  70   a  is covered with the blocking insulating film  33 . 
     The blocking insulating film  33  has a corner  33   b  provided along the corner  70   a  of the electrode layer  70 ; and the corner  33   b  protrudes in the stacking direction from the end surface of the charge storage film  32  in the stacking direction and is adjacent to the air gap  40   b  between the charge storage films  32 . 
     The semiconductor film  20 , the memory film  30 , and the electrode layer  70  are included in a memory cell MC. One memory cell MC in  FIG. 12  is illustrated schematically by a broken line. The memory cell MC has a vertical transistor structure in which the electrode layer  70  surrounds, with the memory film  30  interposed, the periphery of the semiconductor film  20 . 
     In the memory cell MC having the vertical transistor structure, the semiconductor film  20  functions as a channel; and the electrode layer  70  functions as a control gate. The charge storage film  32  functions as a data storage layer that stores charge injected from the semiconductor film  20 . 
     The semiconductor memory device of the embodiment is a nonvolatile semiconductor memory device that can freely and electrically erase/program data and can retain the memory content even when the power supply is OFF. 
     The memory cell MC is, for example, a charge trap memory cell. The charge storage film  32  is an insulative film having many trap sites that trap charge and includes, for example, a silicon nitride film. Or, the charge storage film  32  may be a floating gate that is conductive. 
     The tunneling insulating film  31  is used as a potential barrier when the charge is injected from the semiconductor film  20  into the charge storage film  32  or when the charge stored in the charge storage film  32  is released into the semiconductor film  20 . The tunneling insulating film  31  includes, for example, a silicon oxide film. 
     The blocking insulating film  33  prevents the charge stored in the charge storage film  32  from being released into the electrode layers  70 . Also, the blocking insulating film  33  suppresses back-tunneling of electrons from the electrode layer  70  in the erasing operation. The blocking insulating film  33  includes, for example, at least one of a silicon oxide film and a metal oxide film. 
     The memory film  30  is provided between the inner circumferential surface of the electrode layer  70  and the outer circumferential surface of the semiconductor film  20  opposing the inner circumferential surface of the electrode layer  70 . The outer circumferential surface of the semiconductor film  20  is not exposed in the air gap  40   b  and is covered with and protected by the tunneling insulating film  31 . 
     A film is provided to be continuous between the inner circumferential surface of the electrode layer  70  and the outer circumferential surface of the semiconductor film  20  in a direction connecting the inner circumferential surface to the outer circumferential surface. The electrode layers  70  are physically connected to the columnar unit CL via the film and are supported by the columnar unit CL. 
     As shown in  FIG. 10 , a drain-side select transistor STD is provided at the upper end portion of the columnar unit CL; and a source-side select transistor STS is provided at the lower end portion of the columnar unit CL. For example, the electrode layer  70  of the lowermost layer functions as a control gate of the source-side select transistor STS. For example, the electrode layer  70  of the uppermost layer functions as a control gate of the drain-side select transistor STD. 
     The plurality of memory cells MC are provided between the drain-side select transistor STD and the source-side select transistor STS. The memory cells MC, the drain-side select transistor STD, and the source-side selection transistor STS are connected in series via the semiconductor film  20  and are included in one memory string. For example, the memory strings have a staggered arrangement in a surface direction parallel to the X-Y plane; and the memory cells MC are provided three-dimensionally in the X-direction, the Y-direction, and the Z-direction. 
     As shown in  FIG. 11 , the insulating film  63  is provided on the side surface of the interconnect unit LI dividing the stacked body  100  in the Y-direction. The insulating film  63  is provided between the stacked body  100  and the interconnect unit LI. 
     The interconnect unit LI is, for example, a metal film containing tungsten as a major component. The upper end of the interconnect unit LI is connected to the source line SL provided above the stacked body  100  and shown in  FIG. 10 . As shown in  FIG. 11 , the lower end of the interconnect unit LI contacts the substrate  10 . Also, the lower end of the semiconductor film  20  contacts the substrate  10 . The substrate  10  is, for example, a silicon substrate doped with an impurity. Accordingly, the lower end of the semiconductor film  20  is electrically connectable to the source line SL via the substrate  10  and the interconnect unit LI. 
     As shown in  FIG. 11 , semiconductor regions  81  are formed in the surface of the substrate  10  reached by the lower ends of the interconnect units LI. The plurality of semiconductor regions  81  are provided to correspond to the plurality of interconnect units LI. The plurality of semiconductor regions  81  include a p-type semiconductor region  81  and an n-type semiconductor region  81 . The p-type semiconductor region  81  supplies holes to the semiconductor film  20  via the substrate  10  in the erasing operation. In the read-out operation, electrons are supplied from the interconnect unit LI to the semiconductor film  20  via the n-type semiconductor region  81  and the substrate  10 . 
     By controlling the potential applied to the electrode layer  70  of the lowermost layer provided on the surface (the major surface) of the substrate  10  with the insulating film  41  interposed, a channel is induced in the surface of the substrate  10  between the semiconductor region  81  and the lower end of the semiconductor film  20 . And a current can be caused to flow between the semiconductor region  81  and the lower end of the semiconductor film  20 . 
     The electrode layer  70  of the lowermost layer functions as a control gate for inducing the channel in the surface of the substrate  10 ; and the insulating film  41  functions as a gate insulator film. Because the insulating film  41  which has a dielectric constant that is higher than that of air is between the surface of the substrate  10  and the electrode layer  70  of the lowermost layer instead of the air gap, high-speed operations are possible due to the capacitive coupling between the electrode layer  70  of the lowermost layer and the surface of the substrate  10 . 
     On the other hand, the air gap  40   a  is made between the electrode layers  70  which are the control gates of the memory cells adjacent to each other in the stacking direction (the Z-direction). Therefore, the interconnect capacitance between the electrode layers  70  above and below can be reduced; and high-speed operations of the memory cell MC are possible. Further, interference between adjacent cells such as threshold fluctuation due to capacitive coupling between the electrode layers  70  above and below, etc., can be suppressed. 
     Also, because the charge storage film  32  is divided in the stacking direction as shown in  FIG. 12 , the charge that is stored in the charge storage film  32  does not escape in the stacking direction; and the charge retention characteristics of the memory cell MC are superior. 
     Further, because the charge storage film  32  is provided to oppose only the side surface  70   b  of the surface of the electrode layer  70  on the columnar unit CL side, the charge can be stored in the memory cell MC exclusively in the charge storage film  32  at the position where the electrode layer  70  and the semiconductor film  20  oppose; and the efficiency of the erasing/programming of the data from and to the memory cell MC is increased. 
     Also, because blocking insulating films  33  and electrode layers  70  above and below are formed without the charge storage film  32  being interposed, the total film thickness of the stacked body  100  can be set to be thin; and, for example, the processing is easy for a memory hole MH described below forming the columnar unit CL extending through the stacked body  100  and the like. 
     The blocking insulating film  33  is provided not only on the side surface  70   b  of the electrode layer  70  opposing the charge storage film  32  but also on one portion of the surface  70   c  that is continuous, with the corner  70   a  interposed, from the side surface  70   b . In other words, the surface of the electrode layer  70  on the columnar unit CL side including the corner  70   a  is covered with the blocking insulating film  33 . The blocking insulating film  33  thus formed reliably prevents the diffusion of the elements (e.g., metallic elements) and electrons included in the electrode layer  70  into the charge storage film  32 , the tunneling insulating film  31 , or the semiconductor film  20 . 
     The blocking insulating film  33  is not formed on the entire surface  70   c  of the electrode layer  70 ; and the electrode layer  70  also includes a portion that opposes the electrode layer  70  above or below without the blocking insulating film  33  being interposed. By limiting the portion of the surface  70   c  of the electrode layer  70  where the blocking insulating film  33  is formed to be one portion on the columnar unit CL side, the capacitance increase between the electrode layers  70  above and below can be suppressed. 
     A method for forming the memory cell array  1  of the semiconductor device of the second embodiment will now be described with reference to  FIG. 13  to  FIG. 33B . 
     As shown in  FIG. 13 , the stacked body  100  is formed on the substrate  10 . The substrate  10  is, for example, a semiconductor substrate and is a silicon substrate. 
     The insulating film  41  is formed on a major surface (the surface) of the substrate  10 ; and the electrode layer  70  as a first material layer and a sacrificial layer  44  as a second material layer are stacked alternately on the insulating film  41 . The processes of alternately stacking the electrode layer  70  and the sacrificial layer  44  is repeated; and the plurality of electrode layers  70  and the plurality of sacrificial layers  44  are formed above the substrate  10 . 
     The electrode layer  70  is, for example, a metal film. For example, the metal film contains mainly tungsten or molybdenum. The sacrificial layer  44  is, for example, a silicon oxide film. Or, the sacrificial layer  44  is a different type of metal film from the electrode layer  70 . For example, the electrode layer  70  is a tungsten film; and the sacrificial layer  44  is a molybdenum film. 
     The electrode layer  70  of the lowermost layer is formed on the insulating film  41 ; and the sacrificial layer  44  of the lowermost layer is formed on the electrode layer  70  of the lowermost layer. The insulating film  42  is formed on the electrode layer  70  of the uppermost layer. 
     Then, a plurality of memory holes MH are made in the stacked body  100  as shown in  FIG. 14 . The memory holes MH are made by RIE using a not-shown mask. The memory holes MH extend in the stacking direction of the stacked body  100 , pierce the stacked body  100 , and reach the substrate  10 . 
     After making the memory holes MH, the processes of the first embodiment described above are applicable to the stacked body  100 . 
       FIG. 24A  to  FIG. 27B  are enlarged cross sections of a portion including two layers of the electrode layers  70  and the sacrificial layer  44  or the air gap  40   a  provided between the electrode layers  70  for the stacked body  100  of the second embodiment. 
       FIG. 24A  to  FIG. 27B  may correspond to the processes shown in  FIG. 1A  to  FIG. 4B  of the first embodiment. 
     As shown in  FIG. 24B , the memory hole MH is made on the right side of the cross section shown in  FIG. 24A . 
     The side surfaces of the electrode layers  70  along the memory hole MH and the side surface of the sacrificial layer  44  along the memory hole MH are exposed in the memory hole MH. 
     Then, the sacrificial layer  44  is etched using an etchant or an etching gas supplied to the memory hole MH. For example, the sacrificial layer  44  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the memory hole MH. The electrode layers  70  have etching resistance to the etchant containing hydrofluoric acid and are, for example, metal films. 
     The etching of the sacrificial layer  44  progresses from the side surface of the sacrificial layer  44  exposed in the memory hole MH; and the side surface of the sacrificial layer  44  recedes in the diametral direction of the memory hole MH to be separated from the central axis of the memory hole MH as shown in  FIG. 24C  and  FIG. 15 . 
     By the etching of the sacrificial layer  44 , an air gap  46  that communicates with the memory hole MH is made between the electrode layer  70  and the electrode layer  70  adjacent to each other above and below. One portion of the sacrificial layer  44  remains between the electrode layer  70  and the electrode layer  70 . The air gap  46  is made between the memory hole MH and one portion of the remaining sacrificial layer  44 . The air gap  46  is made in a ring configuration surrounding the periphery of the memory hole MH. 
     Then, the blocking insulating film  33  shown in  FIG. 25A  is formed in the air gap  46  by CVD or ALD. The source gas in the film formation is supplied to the air gap  46  through the memory hole MH. The blocking insulating film  33  is formed also on the side surfaces of the electrode layers  70  adjacent to the memory hole MH. 
     The blocking insulating film  33  is formed conformally along the side surfaces of the electrode layers  70 , the surfaces of the electrode layers  70  adjacent to the air gap  46 , and the side surface of the sacrificial layer  44  adjacent to the air gap  46 . 
     The film thickness of the blocking insulating film  33  is set to be thinner than ½ of the height (the length in the stacking direction) of the air gap  46 . Therefore, one portion  46   a  of the air gap  46  remains between the blocking insulating film  33  formed on the lower surface of the electrode layer  70  on the upper side and the blocking insulating film  33  formed on the upper surface of the electrode layer  70  on the lower side. 
     The remaining air gap  46   a  communicates with the memory hole MH and extends from the memory hole MH toward the sacrificial layer  44 . 
     Then, the charge storage film  32  shown in  FIG. 25B  is formed in the air gap  46   a  and on the side surface of the blocking insulating film  33  adjacent to the memory hole MH. The charge storage film  32  includes a first portion  32   a  filled into the air gap  46   a , and a second portion  32   b  extending in the stacking direction of the stacked body  100  and provided on the side surface of the blocking insulating film  33 . 
     The first portion  32   a  is provided as one body with the second portion  32   b  and extends from the second portion  32   b  toward the sacrificial layer  44 . The first portion  32   a  is provided between the blocking insulating film  33  provided on the lower surface of the electrode layer  70  on the upper side and the blocking insulating film  33  provided on the upper surface of the electrode layer  70  on the lower side. 
     The tunneling insulating film  31  is formed on the side surface of the second portion  32   b  of the charge storage film  32  adjacent to the memory hole MH. The tunneling insulating film  31  extends continuously in the stacking direction of the stacked body  100 . 
     Thus, the memory film  30  that includes the blocking insulating film  33 , the charge storage film  32 , and the tunneling insulating film  31  is formed on the side surface of the memory hole MH. 
     As shown in  FIG. 16 , the memory film  30  is formed also on the bottoms of the memory holes MH. As shown in  FIG. 17 , a cover film  20   a  is formed on the inner side of the memory film  30 . 
     As shown in  FIG. 18 , a mask layer  45  is formed on the upper surface of the stacked body  100 ; and the cover film  20   a  and the memory film  30  that are formed on the bottoms of the memory holes MH are removed by RIE. In the RIE, the memory film  30  formed on the side surfaces of the memory holes MH is covered with and protected by the cover film  20   a . Accordingly, the memory film  30  formed on the side surfaces of the memory holes MH is not damaged by the RIE. 
     After removing the mask layer  45 , a semiconductor film  20   b  is formed inside the memory holes MH as shown in  FIG. 19 . The semiconductor film  20   b  is formed on the side surface of the cover film  20   a  and the bottoms of the memory holes MH where the substrate  10  is exposed. 
     For example, the cover film  20   a  and the semiconductor film  20   b  are crystallized into polycrystalline silicon films by thermal annealing after being formed as amorphous silicon films. The cover film  20   a  is included with the semiconductor film  20   b  in one portion of the semiconductor film  20  described above. 
     As shown in  FIG. 20 , the core film  50  is formed on the inner side of the semiconductor film  20   b ; and the columnar units CL are formed thereby.  FIG. 25B  corresponds to an enlarged view of one portion of  FIG. 20 . 
     The films deposited on the insulating film  42  shown in  FIG. 20  are removed by CMP and etch-back. Subsequently, as shown in  FIG. 21 , the insulating film  43  is formed on the insulating film  42 . The insulating film  43  covers the upper ends of the stacked films included in the columnar units CL. 
     Then, a plurality of slits ST are made in the stacked body  100  including the insulating films  43  and  42 , the electrode layers  70 , the sacrificial layers  44 , and the insulating film  41  by RIE using a not-shown mask. As shown in  FIG. 21 , the slits ST extend in the stacking direction of the stacked body  100 , pierce the stacked body  100 , and reach the substrate  10 . Also, the slits ST extend into the page surface (in  FIG. 10 , the X-direction) and divide the stacked body  100  into a plurality. 
     Impurities are implanted into the substrate  10  exposed at the bottoms of the slits ST by ion implantation; and the p-type or n-type semiconductor region  81  is formed in the surface of the substrate  10  at the bottoms of the slits ST. 
       FIG. 26A  corresponds to an enlarged view of one portion of  FIG. 21 . The slit ST is made in the region of the stacked body  100  where the sacrificial layer  44  remains. 
     The side surfaces of the electrode layers  70  along the slit ST and the side surface of the sacrificial layer  44  along the slit ST are exposed in the slit ST. 
     Then, the sacrificial layer  44  that remains between the electrode layer  70  and the electrode layer  70  is etched using an etchant or an etching gas supplied to the slit ST. For example, the sacrificial layer  44  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the slit ST. 
     By the etching of the sacrificial layer  44 , the air gap  40   a  that communicates with the slit ST is made between the electrode layers  70  adjacent to each other above and below as shown in  FIG. 22  and  FIG. 26B . 
     The etching selectivity of the sacrificial layer  44  with respect to the substrate  10 , the insulating films  41 ,  42 , and  43 , and the electrode layers  70  shown in  FIG. 22  is sufficiently high. The substrate  10 , the insulating films  41 ,  42 , and  43 , and the electrode layers  70  remain without being etched. Also, because the upper ends of the columnar units CL are covered with the insulating film  43 , etching from the upper end side of the columnar units CL also can be suppressed. 
     The electrode layers  70  that are stacked with the air gap  40   a  interposed are supported by the columnar unit CL. The lower end of the columnar unit CL is supported by the substrate  10 ; and the upper end of the columnar unit CL is supported by the insulating films  42  and  43 . 
     As shown in  FIG. 26B , an end portion  33   a  of the blocking insulating film  33  is exposed in the air gap  40   a . Etching of the blocking insulating film  33  is caused to progress from the end portion  33   a ; and the first portion  32   a  of the charge storage film  32  is exposed as shown in  FIG. 27A . 
     For example, the blocking insulating film  33  which is a silicon oxide film is etched by supplying an etchant containing hydrofluoric acid to the slit ST. For example, the charge storage film  32  which is a silicon nitride film has etching resistance to the etchant containing hydrofluoric acid. 
     As shown in  FIG. 27A , the electrode layer  70  has the corner  70   a  between the side surface of the electrode layer  70  on the columnar unit CL side and the surfaces of the electrode layer  70  opposing the other electrode layers  70  adjacent above and below. The side surface of the electrode layer  70  is continuous, with the corner  70   a  interposed, with the surface of the electrode layer  70  opposing the other electrode layer  70 . 
     The blocking insulating film  33  has the corner  33   b  formed along the corner  70   a  of the electrode layer  70  and covering the corner  70   a . The base of the first portion  32   a  of the charge storage film  32  on the second portion  32   b  side is interposed in the vertical direction between the corner  33   b  of the blocking insulating film  33  provided on the lower surface of the electrode layer  70  on the upper side and the corner  33   b  of the blocking insulating film  33  provided on the upper surface of the electrode layer  70  on the lower side. The first portion  32   a  and the second portion  32   b  of the charge storage film  32  are continuous along the corner  33   b  of the blocking insulating film  33  and cover the corner  33   b.    
     The etching of the blocking insulating film  33  is stopped at a timing when one portion on the tip side of the first portion  32   a  of the charge storage film  32  is exposed. The corners  33   b  of the blocking insulating films  33  remain at this point in time. 
     Then, etching of the charge storage film  32  is caused to progress from the exposed first portion  32   a . For example, the charge storage film  32  which is a silicon nitride film is etched by supplying an etchant containing phosphoric acid to the slit ST. The blocking insulating film  33  and the electrode layer  70  have etching resistance to the etchant containing phosphoric acid. 
     The first portion  32   a  of the charge storage film  32  is etched and removed; and the air gap  40   c  is made between the blocking insulating film  33  formed on the lower surface of the electrode layer  70  on the upper side and the blocking insulating film  33  formed on the upper surface of the electrode layer  70  on the lower side as shown in  FIG. 27B . 
     After the first portion  32   a  is removed, the second portion  32   b  that is formed on the side surface of the blocking insulating film  33  is divided in the stacking direction by causing the etching of the charge storage film  32  to progress further. At this time, the tunneling insulating film  31  functions as an etching stopper; and the etchant does not flow around to the back surface (the surface on the side opposite to the interface with the blocking insulating film  33 ) side of the second portion  32   b.    
     The air gap  40   b  is made in the second portion  32   b  of the charge storage film  32  that was continuous in the stacking direction of the stacked body  100 ; and the second portion  32   b  is divided in the stacking direction of the stacked body  100  with the air gap  40   b  interposed. 
     As shown in  FIG. 27A , the corner  33   b  of the blocking insulating film  33  covering the corner  70   a  of the electrode layer  70  is separated from the corner  70   a  of the electrode layer  70  by an amount corresponding to the film thickness of the blocking insulating film  33 . 
     After the first portion  32   a  of the charge storage film  32  interposed between the blocking insulating films  33  disappears, etching of the second portion  32   b  progresses isotropically from the corners  33   b  of the blocking insulating films  33  as start points; and the second portion  32   b  is divided in the stacking direction (the vertical direction) of the stacked body  100 . 
     In the second embodiment as well, similarly to the first embodiment, the etching start point of the second portion  32   b  is not proximal to the side surface of the electrode layer  70 ; and there is a distance from the etching start point to the portion of the second portion  32   b  opposing the side surface of the electrode layer  70 . It is desirable for the distance to be not less than the film thickness of the second portion  32   b.    
     Therefore, the second portion  32   b  can be divided in the vertical direction before the etching progresses to the portion of the second portion  32   b  opposing the side surface of the electrode layer  70 . Or, the etching consumption amount can be suppressed for the portion of the second portion  32   b  opposing the side surface of the electrode layer  70  until the dividing of the second portion  32   b  in the vertical direction ends. The charge storage film  32  can be divided in the vertical direction while causing a sufficient amount of the charge storage film  32  to remain at the portion opposing the side surface of the electrode layer  70 . 
     By etching the end portion  33   a  of the blocking insulating film  33  covering the tip portion of the first portion  32   a  of the charge storage film  32  in  FIG. 26B , the blocking insulating film  33  also is divided in the stacking direction (the vertical direction) of the stacked body  100  as shown in  FIG. 27A . Further, by the first portion  32   a  disappearing, the air gap  40   c  is made as shown in  FIG. 27B  between the blocking insulating films  33  adjacent to each other in the vertical direction. 
     Even after the etching to divide the second portion  32   b  of the charge storage film  32  has ended, the corners  33   b  of the blocking insulating films  33  and the portions of the blocking insulating films  33  extending along the side surfaces of the electrode layers  70  from the corners  33   b  remain as shown in  FIG. 27B . The corners  33   b  of the blocking insulating films  33  are adjacent to the air gap  40   b  between the multiple second portions  32   b  that are separated. 
     Accordingly, the etching of the second portion  32   b  of the charge storage film  32  can be prevented from progressing from portions other than the portions proximal to the corner  33   b  of the blocking insulating film  33 . The charge storage film  32  can be caused to remain reliably at the portion opposing the side surface of the electrode layer  70 . 
     The corner  33   b  of the blocking insulating film  33  and the portion of the blocking insulating film  33  extending from the corner  33   b  toward the air gap  40   a  may be removed as shown in  FIG. 28A . For example, the portion of the blocking insulating film  33  recited above can be removed by an etchant or an etching gas supplied to the air gap  40   a  through the slit ST. 
     Subsequently, as shown in  FIG. 28B , a protective film  64  may be formed on the surfaces of the electrode layers  70  exposed in the air gap  40   a . For example, when forming the insulating film  63  described below on the side surface of the slit ST, one portion of the insulating film  63  can be formed on the surfaces of the electrode layers  70  as the protective film  64 . 
     The insulating film  63  is formed on the side surface and bottom of the slit ST as shown in  FIG. 23 . The insulating film  63  that has poor coverage plugs the opening of the air gap  40   a  on the slit ST side. The interior of the air gap  40   a  is not filled with the insulating film  63 . 
     After removing the insulating film  63  formed on the bottom of the slit ST by RIE, the interconnect unit LI is filled into the slit ST as shown in  FIG. 11 . The lower end of the interconnect unit LI is connected to the substrate  10  via the semiconductor region  81 . Subsequently, the bit lines BL, the source line SL, etc., shown in  FIG. 10  are formed. 
     The processes shown in  FIG. 5A  to  FIG. 8  described in the first embodiment described above also are applicable to the method for manufacturing the semiconductor device of the second embodiment. 
     In  FIG. 8 , the first layer  171  and the second layer  172  can correspond to electrode layers, the first film  133  can correspond to a blocking insulating film, the second film  132  can correspond to a charge storage film, and the third film  131  can correspond to a tunneling insulating film. 
       FIG. 35A  to  FIG. 38B  are schematic cross-sectional views of a method for manufacturing a semiconductor device of a reference example. 
       FIG. 35A  and  FIG. 35B  correspond to the process shown in  FIG. 24C . 
       FIG. 36A  and  FIG. 36B  correspond to the process shown in  FIG. 26B . 
       FIG. 37A  and  FIG. 37B  correspond to the process shown in  FIG. 27A . 
       FIG. 38A  and  FIG. 38B  correspond to the process shown in  FIG. 27B . 
     The electrode layers  70  shown in  FIG. 35A ,  FIG. 36A ,  FIG. 37A , and  FIG. 38A  are provided on the upper layer side of the electrode layers  70  shown in  FIG. 35B ,  FIG. 36B ,  FIG. 37B , and  FIG. 38B . For example,  FIG. 35A ,  FIG. 36A ,  FIG. 37A , and  FIG. 38A  show one portion of the stacked body  100  on the top side of the memory hole MH; and  FIG. 35B ,  FIG. 36B ,  FIG. 37B , and  FIG. 38B  show one portion of the stacked body  100  on the bottom side of the memory hole MH. 
     One portion of the sacrificial layer  44  is removed as shown in  FIG. 35A  and  FIG. 35B  by an etchant or an etching gas supplied from the memory hole MH; and the air gap  46  that communicates with the memory hole MH is made between the electrode layers  70 . 
     In particular, the amount of the etchant or the etching gas supplied to the bottom side of the memory hole MH easily becomes less than the amount of the etchant or the etching gas supplied to the top side of the memory hole MH as the aspect ratio of the memory hole MH becomes high. Also, the time that the sacrificial layer  44  on the bottom side of the memory hole MH is exposed to the etchant or the etching gas easily becomes shorter than the time that the sacrificial layer  44  on the top side of the memory hole MH is exposed to the etchant or the etching gas. 
     Therefore, the receded amount from the side surface of the memory hole MH of the sacrificial layer  44  on the bottom side of the memory hole MH becomes less than the receded amount from the side surface of the memory hole MH of the sacrificial layer  44  on the top side of the memory hole MH; and a width b of the air gap  46  on the bottom side shown in  FIG. 35B  easily becomes narrower than a width a of the air gap  46  on the top side shown in  FIG. 35A . 
     The blocking insulating film  33  and the first portion  32   a  of the charge storage film  32  are formed in the air gap  46  as shown in  FIG. 36A  and  FIG. 36B . Further, the tunneling insulating film  31 , the semiconductor film  20 , and the core film  50  are formed. Subsequently, the slit ST is made. Then, the air gap  40   a  is made by removing the sacrificial layer  44  remaining between the electrode layers  70  through the slit ST. 
     Subsequently, as shown in  FIG. 37A  and  FIG. 37B , the blocking insulating film  33  is etched; and one portion of the first portion  32   a  of the charge storage film  32  is exposed. Then, etching of the charge storage film  32  is caused to progress from the exposed portion. 
     Here, due to the difference between the width a of the air gap  46  of  FIG. 35A  and the width b of the air gap  46  of  FIG. 35B , the protruding length of the first portion  32   a  from the second portion  32   b  shown in  FIG. 37B  is shorter than the protruding length of the first portion  32   a  from the second portion  32   b  shown in  FIG. 37A . 
     Therefore, a difference of the disappearance time due to the etching of the first portion  32   a  occurs between the top side and the bottom side of the memory hole MH. The first portion  32   a  on the bottom side of the memory hole MH disappears earlier than the first portion  32   a  on the top side; and by this amount, the second portion  32   b  on the bottom side of the memory hole MH starts to be etched earlier than the second portion  32   b  on the top side. 
     For example, there may be cases where the second portion  32   b  cannot yet be divided on the top side shown in  FIG. 38A  at the point in time when the second portion  32   b  on the bottom side shown in  FIG. 38B  is divided in the vertical direction. Subsequently, as the etching continues further to divide the second portion  32   b  on the top side, the recession in the vertical direction of the second portion  32   b  on the bottom side progresses further; and the amount of the second portion  32   b  at the portion opposing the side surface of the electrode layer  70  may undesirably decrease or disappear. 
     Therefore, according to the method of the embodiment shown in  FIG. 29A  to  FIG. 33B  described below, the charge storage film  32  can be caused to remain reliably on the side surface of the electrode layer  70  even in the case where the receded amount of the sacrificial layer  44  from the memory hole MH fluctuates between the stacking positions of the sacrificial layer  44 . 
     The electrode layers  70  shown in  FIG. 29A ,  FIG. 30A ,  FIG. 31A ,  FIG. 32A , and  FIG. 33A  are provided on the upper layer side of the electrode layers  70  shown in  FIG. 29B ,  FIG. 30B ,  FIG. 31B ,  FIG. 32B , and  FIG. 33B . For example,  FIG. 29A ,  FIG. 30A ,  FIG. 31A ,  FIG. 32A , and  FIG. 32A  show one portion of the stacked body  100  on the top side of the memory hole MH; and  FIG. 29B ,  FIG. 30B ,  FIG. 31B ,  FIG. 32B , and  FIG. 33B  show one portion of the stacked body  100  on the bottom side of the memory hole MH. 
     The air gap  46  that communicates with the memory hole MH is made between the electrode layers  70  by one portion of the sacrificial layer  44  being removed as shown in  FIG. 29A  and  FIG. 29B  by an etchant or an etching gas supplied from the memory hole MH. 
     The receded amount from the side surface of the memory hole MH of the sacrificial layer  44  on the bottom side of the memory hole MH is less than the receded amount from the side surface of the memory hole MH of the sacrificial layer  44  on the top side of the memory hole MH; and the width b of the air gap  46  on the bottom side shown in  FIG. 29B  is narrower than the width a of the air gap  46  on the top side shown in  FIG. 29A . 
     As shown in  FIG. 30A  and  FIG. 30B , the blocking insulating film  33  and the first portion  32   a  of the charge storage film  32  are formed in the air gap  46 . Further, the tunneling insulating film  31 , the semiconductor film  20 , and the core film  50  are formed. Subsequently, the slit ST is made. Then, the air gap  40   a  is made by removing the sacrificial layer  44  remaining between the electrode layers  70  through the slit ST. 
     Here, the blocking insulating film  33  is a stacked film of a first blocking film  34  and a second blocking film  35 . First, the first blocking film  34  is formed conformally on the side surface of the electrode layer  70  and the inner surface of the air gap  46 ; and the second blocking film  35  is formed conformally on the inner side of the first blocking film  34 . An air gap that extends from the memory hole MH to the sacrificial layer  44  side remains on the inner side of the second blocking film  35 ; and the first portion  32   a  of the charge storage film  32  is filled into the air gap. The second portion  32   b  of the charge storage film  32  is formed on the side surface of the second blocking film  35 . 
     The first blocking film  34  and the second blocking film  35  are films of different types of materials; for example, the first blocking film  34  is a metal oxide film; and the second blocking film  35  is a silicon oxide film. For example, the blocking property of the electrons can be higher for such a blocking insulating film  33  which is a stacked film than for the blocking insulating film  33  which is a single-layer silicon oxide film. 
     Subsequently, as shown in  FIG. 31A  and  FIG. 31B , one portion of the second blocking film  35  is exposed by etching the first blocking film  34 . The first blocking film  34  is divided in the vertical direction. At this time, the first blocking film  34  has high etching selectivity with respect to the electrode layer  70  and the second blocking film  35 . 
     Subsequently, as shown in  FIG. 32A  and  FIG. 32B , one portion of the first portion  32   a  of the charge storage film  32  is exposed by etching the second blocking film  35 . The second blocking film  35  is divided in the vertical direction. At this time, the second blocking film  35  has high etching selectivity with respect to the electrode layers  70  and the charge storage film  32 . Then, etching of the charge storage film  32  is caused to progress from the exposed portion of the first portion  32   a.    
     Here, due to the difference between the width a of the air gap  46  of  FIG. 29A  and the width b of the air gap  46  of  FIG. 29B , the protruding length of the first portion  32   a  from the second portion  32   b  shown in  FIG. 32B  is shorter than the protruding length of the first portion  32   a  from the second portion  32   b  shown in  FIG. 32A . 
     Therefore, a difference of the disappearance time due to the etching of the first portion  32   a  occurs between the top side and the bottom side of the memory hole MH. The first portion  32   a  on the bottom side of the memory hole MH disappears earlier than the first portion  32   a  on the top side; and by this amount, the second portion  32   b  on the bottom side of the memory hole MH starts to be etched earlier than the second portion  32   b  on the top side. 
     Etching of the second portion  32   b  progresses isotropically from the corners  35   a  of the second blocking films  35  as start points; and the second portion  32   b  is divided in the vertical direction as shown in  FIG. 33A  and  FIG. 33B . 
     According to the example shown in  FIG. 29A  to  FIG. 33B , the blocking insulating film  33  that is not a single layer but is two layers is interposed between the electrode layer  70  and the charge storage film  32 . Therefore, the corner  35   a  of the second blocking film  35  is more distal to the corner  70   a  of the electrode layer  70  than is a corner  34   a  of the first blocking film  34 . In other words, the etching start point of the second portion  32   b  can be set to be separated from the corner  70   a  of the electrode layer  70 . The distance that the second portion  32   b  recedes from the etching start point to the portion opposing the side surface of the electrode layer  70  can be lengthened. 
     Accordingly, even in the case where the etching of the second portion  32   b  starts earlier on the bottom side shown in  FIG. 33B  than on the top side shown in  FIG. 33A , a sufficient amount of the second portion  32   b  can remain at the portion opposing the side surface of the electrode layer  70  on the bottom side when the second portion  32   b  on the top side is divided in the vertical direction. 
     At this time, the height (the length in the vertical direction) of the air gap  40   b  dividing the second portion  32   b  in the vertical direction on the bottom side is larger than the height (the length in the vertical direction) of the air gap  40   b  dividing the second portion  32   b  in the vertical direction on the top side. 
     In the example shown in  FIG. 24A  to  FIG. 28B  recited above, the blocking insulating film  33  corresponds to the first insulating film; the charge storage film  32  corresponds to the second insulating film; and the tunneling insulating film  31  corresponds to the third insulating film. 
     However, the film  33  used as the first insulating film may be a film including a charge storage film. The film  33  can be a stacked film including two types of films as shown in  FIG. 30A  to  FIG. 33B . For example, the film  33  used as the first insulating film can be a stacked film of a blocking insulating film and a charge storage film. Because the film  33  also is divided in the vertical direction, the movement in the vertical direction of the charge stored in the charge storage film can be prevented even in the case where the film  33  is the film including the charge storage film. 
     Also, the film  32  used as the second insulating film may be a tunneling insulating film; and the semiconductor film  20  may be formed without the film  31  used as the third insulating film being interposed at the side surface of the film  32 . Or, the tunneling insulating film may be a stacked film including the film  32  and the film  31 . 
     Next, a method for forming a memory cell array of a semiconductor device of a third embodiment will now be described with reference to  FIG. 39A  to  FIG. 45 . 
       FIGS. 39A to 45  are schematic cross-sectional views showing a portion of the stacked body  100  on the substrate  10 . 
     A first material layer  71  and a second material layer  44  are stacked alternately on the substrate  10 . The processes of alternately stacking the first material layer  71  and the second material layer  44  are repeated, and a plurality of first material layers  71  and a plurality of second material layers  44  are formed on the substrate  10 . 
     The first material layer  71  is, for example, a silicon nitride layer. 
     The second material layer  44  is, for example, a boron-silicate glass (BSG) layer which is a silicon oxide layer doped with boron. 
     The memory hole MH is made in the stacked body  100  including the plurality of first material layers  71  and the plurality of second material layers  44 , as shown in  FIG. 39A . The memory hole MH is made, for example, by RIE using a not-shown mask including a carbon layer, and a CF based gas. The memory hole MH pierces the plurality of first material layers  71  and the plurality of second material layers  44 . 
     After making the memory hole MH, the second material layer  44  which is a BSG layer is etched using an etchant, for example, containing dilute hydrofluoric acid supplied to the memory hole MH. 
     A side etching of the second material layer  44  progresses from a side surface of the second material layer  44  exposed in the memory hole MH; and the side surface of the second material layer  44  recedes in the diametral direction of the memory hole MH to be separated from the central axis of the memory hole MH as shown in  FIG. 39B . 
     By the etching of the second material layer  44 , a gap  46  that communicates with the memory hole MH is made between memory hole MH side ends of first material layers  71  adjacent to each other above and below. One portion of the second material layer  44  remains between the first material layer  71  and the first material layer  71 . The gap  46  is made in a ring configuration surrounding the periphery of the memory hole MH. 
     Then, the second blocking film  35  shown in  FIG. 40A  is formed in the gap  46  by, for example, ALD. The second blocking film  35  is, for example, a silicon oxide film containing SiO 2  as a major component. 
     The second blocking film  35  is formed also on the side surfaces of the first material layers  71  exposed in the memory hole MH. The second blocking film  35  is formed conformally along the side surfaces of the first material layers  71 , surfaces of the first material layers  71  exposed in the gap  46 , and the side surfaces of the second material layers  44  exposed in the gap  46 . 
     The second blocking film  35  is formed along a stepped portion between the side surface of the first material layer  71  and the side surface of the second material layer  44 . 
     The film thickness of the second blocking film  35  is set to be thinner than ½ of the height of the gap  46 . Therefore, a gap  47  remains between the second blocking film  35  formed on the lower surface of the first material layer  71  on the upper side and the second blocking film  35  formed on the upper surface of the first material layer  71  on the lower side, as shown in  FIG. 40A . The gap  47  communicates with the memory hole MH and extends in a protruding configuration from the memory hole MH towards the second material layer  44 . 
     Then, the charge storage film  32  shown in  FIG. 40B  is formed on the side surface of the second blocking film  35  exposed in the memory hole MH and in the gaps  47  by, for example, ALD. The charge storage film  32  is, for example, a silicon nitride film. 
     The second blocking film  35  has a stepped portion that reflects the stepped portion between the side surface of the first material layer  71  and the side surface of the second material layer  44 . The charge storage film  32  is formed along the stepped portion of the second blocking film  35  continuously in the stacking direction of the stacked body  100 . 
     The film thickness of the charge storage films  32  is set to be thinner than ½ of the height of the gap  47 . Therefore, as shown in  FIG. 40B , a gap  48  remains memory at a hole MH side of the charge storage film  32  that enters into a portion opposing to the side surface of the second material layer  44 . The gap  48  communicates with the memory hole MH and extends in a protruding configuration from the memory hole MH towards the second material layer  44 . 
     Then, the tunneling insulating film  31  shown in  FIG. 41A  is formed on the side surface of the charge storage film  32  exposed in the memory hole MH and on the gaps  48  by, for example, ALD. The tunneling insulating film  31  is, for example, a silicon oxide film. 
     The tunneling insulating film  31  is filled in the gap  48  and extends continuously in the stacking direction of the stacked body  100 . A stepped portion is not formed on the side surface of the tunneling insulating film  31  exposed in the memory hole MH. 
     The semiconductor film  20  shown in  FIG. 41A  is formed on the side surface of the tunneling insulating film  31  by, for example, CVD. The semiconductor film  20  extends continuously in the stacking direction of the stacked body  100 . 
     For example, the semiconductor film  20  is crystallized into polycrystalline silicon films by thermal annealing after being formed as amorphous silicon films. 
     The core film  50  shown in  FIG. 41A  is formed on the inner side of the semiconductor film  20 . The core film  50  is, for example, a silicon oxide film. 
     Then, the slit ST is made in the stacked body  100  as shown in  FIG. 41B  by RIE using not-shown mask including carbon layer, and CF based gas. The slit extends in the stacking direction of the stacked body  100  and pierces the stacked body  100 . Further, the slit ST extends into the page surface and divides the stacked body  100  into a plurality of blocks. 
     Next, the first material layer  71  which is a silicon nitride layer is removed by an etchant containing, for example, a phosphoric acid supplied to the slit ST. 
     During the etching, the charge storage film  32  which is a silicon nitride film of the same kind as the first material layer  71  is covered with the second blocking film  35  which is a silicon oxide film, and is not etched. 
     The first material layer  71  is removed, and a gap  72  that communicates with the slit ST is made between the second material layers  44  adjacent to each other above and below as shown in  FIG. 42A . 
     The plurality of second material layers  44  that are stacked with the gap  72  interposed are supported by the columnar unit CL including the second blocking film  35 , the charge storage film  32 , the tunneling insulating film  31 , the semiconductor film  20  and the core film  50 . 
     The second material layer  44  and the second blocking film  35  are exposed in the gap  72 . 
     The first blocking film  34 , a metal nitride film  73 , and the electrode layer  70  shown in  FIG. 42B  are formed in this order in the gap  72 . 
     The first blocking film  34  is a metal oxide film and may be, for example, an aluminum oxide film. 
     The first blocking film  34  is formed conformally along an upper surface, a lower surface, and a side surface exposed in the slit ST of the second material layer  44 , and the second blocking film  35  by, for example, ALD. 
     The metal nitride film  73  is formed conformally along the first blocking film  34  on the inner side of the first blocking film  34  by, for example, ALD. The metal nitride film  73  is, for example, a titanium nitride film. 
     The electrode layer  70  is formed on the inner side of the metal nitride film  73  by, for example, CVD. The electrode layer  70  is grown in crystal using the metal nitride film  73  as a seed layer. The electrode layer  70  is, for example, a tungsten layer or a molybdenum layer. 
     The electrode layer  70 , the metal nitride film  73 , and the first blocking film  34  formed on the side surface of the slit ST are removed by, for example, wet-etching, RIE, or chemical dry etching (CDE). 
     The electrode layer  70 , the metal nitride film  73 , and the first blocking film  34  formed on the side surface of the slit ST is removed so that the side surface of the second material layer  44  is exposed in the slit ST. 
     Then, the second material layer  44  which is a BSG layer is removed by the etching through the slit ST. 
     The second material layer  44  is removed, and a gap  40   a  that communicates with the slit ST is made between the electrode layers  70  adjacent to each other above and below as shown in  FIG. 43A . 
     The plurality of the electrode layers  70  are supported by the columnar unit CL and the gap  40   a  between the electrode layers  70  is maintained. The second blocking film  35  is exposed in the gap  40   a.    
     The second material layer  44  is removed by a process using an etchant containing, for example, hydrofluoric acid. The etchant containing hydrofluoric acid can be used in a vapor phase. In the embodiment, the second material layer  44  is removed by vapor phase cleaning (VPC) using a vapor containing hydrofluoric acid. 
     A ratio of an etching rate of the second material layer  44  which is a BSG layer with respect to an etching rate of the second blocking film  35  which is a silicon oxide film containing SiO 2  as a main component is 100 or more in VPC using vapor containing hydrofluoric acid. 
     Therefore, the second material layer  44  can be removed selectively while both of the second material layer  44  and the second blocking film  35  are silicon oxide based material. 
     Then, a portion of the second blocking film  35  exposed in the gap  40   a  is etched. 
     The second blocking film  35  is etched using an etchant including, for example, hydrofluoric acid in liquid phase. Otherwise the second blocking film  35  is etched by VPC using vapor having different hydrofluoric acid concentration from vapor used in the etching of the second material layer  44 . 
     The portion of the second blocking film  35  exposed in the gap  40   a  is etched so that the charge storage film  32  is exposed in the gap  40   a  as shown in  FIG. 43B . The second blocking film  35  is divided in the stacking direction (the vertical direction) of the stacked body  100 . 
     Then, a portion of the charge storage film  32  exposed in the gap  40   a  is etched. The charge storage film  32  which is a silicon nitride film is etched using an etchant containing, for example, phosphoric acid. 
     The portion of the charge storage film  32  exposed in the gap  40   a  is etched so that the tunneling insulating film  31  is exposed in the gap  40   a , as shown in  FIG. 44 . The charge storage film  32  is divided in the stacking direction (the vertical direction) of the stacked body  100 . 
       FIG. 45  is an enlarged view of a portion A shown in  FIG. 44 . 
     According to the embodiment, the gap  46  shown in  FIG. 39B  is made by receding the second material layer  44  after making the memory hole MH. Then, the second blocking film  35  and the charge storage film  32  are introduced into the gap  46 . 
     Then, the etching process that divides the second blocking film  35  and the charge storage film  32  in the vertical direction, is controlled so as to stop during a portion introduced into the gap  46  is etched. Such a control enables to prevent that dispersion in disappearance rate among the second blocking film  35  and the charge storage film  32 , for example, due to the difference of the distances from the slit ST results in the dispersion in etching amount in the vertical direction. 
     Accordingly, the second blocking film  35  and the charge storage film  32  can be remained surely between the electrode layer  70  and the semiconductor film  20 . The lengths of the second blocking film  35  and the charge storage film  32  along the vertical direction remained after dividing is larger than the thickness of the electrode layer  70 . 
     The second blocking film  35  covers a corner  70   a  on the columnar unit CL side of the electrode layer  70  with the metal nitride film  73  and the first blocking film  34  interposed between the second blocking film  35  and the electrode layer  70  in an example shown in  FIG. 45 . Further, the charge storage film  32  remains so as to cover a corner of the second blocking film  35 . A portion  31   a  of the tunneling insulating film  31  is disposed between the charge storage films  32  divided in the vertical direction so as to protrude to the gap  40   a  side. 
     Then, the insulating film  63  is formed on a side surface and a bottom of the slit ST as shown in the  FIG. 23 . The insulating film  63  that has poor coverage plugs the opening of the gap  40   a  on the slit ST side. The interior of the gap  40   a  is not filled with the insulating film  63 . 
     After removing the insulating film  63  formed on the bottom of the slit ST by RIE, the interconnect unit LI is filled into the slit ST as shown in  FIG. 11 . The lower end of the interconnect unit LI is connected to the substrate  10  via the semiconductor region  81 . 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modification as would fall within the scope and spirit of the inventions.