JP2010287724A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor device reducing a contact area between a conductive film plug and a phase changing material layer. <P>SOLUTION: The method of manufacturing the semiconductor device includes the steps of forming a hole portion in a first insulating film, forming the conductive film plug in the hole portion, forming a mask element on an upper surface of the conductive film plug to expose a portion of the upper surface of the conductive film plug, selectively etching the conductive film plug by using the mask element as a mask to reduce the area of the upper surface of the conductive film plug, and forming the phase changing material layer in contact with the reduced upper surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including phase change memory cells.

  In order to meet the demand for speeding up and downsizing of electronic devices, a nonvolatile semiconductor memory device (hereinafter referred to as “phase change memory”) using a phase change material as a storage medium has been developed in recent years. The phase change memory has a phase change material that changes phase by heat and two electrodes for applying Joule heat to the phase change material. In the phase change memory, data is rewritten by controlling two phase states (crystalline state and amorphous state) of the phase change material by switching the application of Joule heat from the electrode to the phase change material. In the phase change memory, it is required to improve the heat generation efficiency of the phase change material because it is necessary to reduce the data rewrite current.

  As one of the methods for improving the extinction efficiency, there is a method of reducing Joule heat necessary for rewriting by reducing a region where a phase change is made in a phase change material. For example, Patent Document 1 (Example 1 and FIGS. 1 to 6) discloses a method of reducing the area where the heater electrode and the phase change material are in contact with each other. The manufacturing method of the phase change memory disclosed in Patent Document 1 is performed as follows. First, a hole is opened in the first insulating film. The opening diameter of the hole is set to a minimum dimension that can be processed by lithography. Next, a second insulating film having a film thickness that does not fill the hole and covering the bottom and side walls of the hole and the first insulating film is formed. Next, the second insulating film is etched back to form sidewall spacers made of the second insulating film on the sidewalls of the hole. The opening diameter of the hole is reduced by the thickness of the sidewall spacer. Next, a TiN film is formed in the reduced hole. Next, this TiN film is polished and removed by a CMP method to form a buried plug made of the TiN film. This embedded plug becomes a heater electrode. Next, a phase change material layer is formed on the embedded plug. According to this method described in Patent Document 1, it is possible to form a heater electrode having an upper surface with a diameter smaller than the minimum dimension that can be processed by lithography.

JP 2008-71797 A

  However, the technique described in Patent Document 1 has the following problems. Sidewall spacers formed on the sidewalls of the holes by etch back tend to have a curved upper surface. That is, the width of the sidewall spacer tends to be thinner toward the upper part of the hole. In the opening diameter of the hole portion in which such a sidewall spacer is formed, the opening diameter of the upper portion of the hole portion is formed larger than the opening diameter of the bottom portion of the hole portion. For this reason, the heater electrode embedded in the hole portion is likely to have a shape in which the upper portion is widened reflecting this sidewall spacer shape. As a result, in the technique described in Patent Document 1, even if the diameter of the bottom surface of the heater electrode is reduced to a manufacturable limit, the diameter of the upper surface of the heater electrode can be formed only to a larger diameter than the bottom surface. Therefore, there is a problem that it is not possible to reduce the size sufficiently.

  According to the first aspect of the present invention, a step of forming a hole in the first insulating film, a step of forming a conductive film plug in the hole, and an upper surface of the conductive film plug are formed on the upper surface of the conductive film plug. The step of forming a mask body so as to be partially exposed, the step of selectively etching the conductive film plug using the mask body as a mask to reduce the area of the upper surface of the conductive film plug, and the reduction And a step of forming a phase change material layer in contact with an upper surface.

  According to a second aspect of the present invention, a step of forming a hole in the first insulating film, a step of forming a conductive film plug in the hole, a top surface of the conductive film plug, A step of forming a mask body so as to be partially exposed; a step of selectively etching the conductive film plug using the mask body as a mask to form a protrusion on the conductive film plug; and a top of the protrusion Forming a phase change material layer so as to be in contact with the region.

  According to the third aspect of the present invention, a step of forming a hole in the first insulating film, a step of forming a conductive film plug in the hole, a top surface of the conductive film plug, A step of forming a mask body so as to cover a portion, a step of selectively etching a portion of the upper portion of the conductive film plug using the mask body as a mask, and an upper surface of the conductive film plug covered by the mask body. And a step of forming a phase change material layer so as to be in contact with at least a part of the semiconductor device.

  In the manufacturing method of the present invention, a conductive film plug (heater electrode plug) is formed in the hole opening in the first insulating film, and a mask body is formed so as to cover a part of the upper surface of the conductive film plug. By partially removing the upper surface of the conductive film by isotropic etching using the body as a mask, the upper surface of the conductive film plug is reduced. Thus, by adjusting the etching amount, the size of the upper surface of the conductive film plug can be reduced to an arbitrary size without limiting the size that can be reduced.

1 is a schematic cross-sectional view of a semiconductor device for explaining a first step in a method for manufacturing a semiconductor device according to Example 1 of the invention. FIG. 5 is a schematic cross-sectional view of a semiconductor device for explaining a second step in the method for manufacturing a semiconductor device according to the first embodiment of the invention. FIG. 5 is a schematic cross-sectional view of a semiconductor device for explaining a third step in the method for manufacturing the semiconductor device according to the first embodiment of the invention. FIG. 5 is a schematic cross-sectional view of a semiconductor device for explaining a fourth step in the method for manufacturing a semiconductor device according to the first embodiment of the invention. FIG. 5 is a schematic cross-sectional view of a semiconductor device for explaining a fifth step in the method for manufacturing the semiconductor device according to the first embodiment of the invention. FIG. 6 is a schematic partial plan view of the semiconductor device shown in FIG. 5. FIG. 6 is a schematic cross-sectional view of a semiconductor device for explaining a sixth step in the method for manufacturing the semiconductor device according to the first embodiment of the invention. FIG. 6 is a schematic cross-sectional view of a semiconductor device for explaining a seventh step in the method for manufacturing the semiconductor device according to the first embodiment of the invention. FIG. 9 is a schematic partial plan view of the semiconductor device shown in FIG. 8. FIG. 7 is a schematic partial plan view of a semiconductor device showing a different form from FIG. 6. FIG. 10 is a schematic partial plan view of a semiconductor device showing a form different from FIG. 9. FIG. 10 is a schematic cross-sectional view of a semiconductor device for illustrating an eighth step in the method for manufacturing the semiconductor device according to the first embodiment of the invention. FIG. 9 is a schematic cross-sectional view of a semiconductor device for explaining a ninth step in the method for manufacturing the semiconductor device according to the first embodiment of the invention. FIG. 10 is a schematic cross-sectional view of a semiconductor device for explaining a tenth step in the method for manufacturing the semiconductor device according to the first embodiment of the invention. FIG. 6 is a schematic cross-sectional view of a semiconductor device for explaining a fifth step in the method for manufacturing the semiconductor device according to the second embodiment of the invention. FIG. 15 is a schematic partial plan view of the semiconductor device shown in FIG. 14. FIG. 10 is a schematic cross-sectional view of a semiconductor device for explaining a sixth step in the method for manufacturing the semiconductor device according to the second embodiment of the invention.

  A method for manufacturing a semiconductor device according to Embodiment 1 of the present invention will be described. 1 to 14 are schematic views for explaining a method for manufacturing a semiconductor device according to Embodiment 1 of the present invention. 1 to 5, 7, 8, and 12 to 14 are schematic cross-sectional views of the semiconductor device. FIG. 6 is a schematic partial plan view of the semiconductor device shown in FIG. FIG. 9 is a schematic partial plan view of the semiconductor device shown in FIG. 10 and 11 are schematic partial plan views of a semiconductor device showing another form different from those in FIGS. 6 and 9. A semiconductor device described below is a semiconductor device including a phase change memory.

  As a first step, a selection transistor or the like for selecting a memory address is formed (FIG. 1). First, the first diffusion layer 3 and the second diffusion layer 4 that become the source region and the drain region, the gate insulating film (not shown), and the gate electrode 5 are formed on the semiconductor substrate 2. Next, the first insulating film layer 6 is formed on the semiconductor substrate 2. Next, a through-hole is formed in the first insulating film layer 6 so that the second diffusion layer 4 is exposed, and a metal is embedded in the through-hole, whereby a second electrically connected to the second diffusion layer 4 is obtained. Contact plug 8 is formed. Further, the first insulating film layer 6 is laminated, a through hole is formed so that the first diffusion layer 3 is exposed, and a metal is embedded in the through hole, whereby the first insulating layer 6 is electrically connected to the first diffusion layer 3. One contact plug 7 is formed. The first contact plug 7 can be formed from a plurality of types of metals. For example, the first contact plug 7 can be formed by stacking and filling a titanium film, a titanium nitride film as a barrier metal, and tungsten in the through hole from the semiconductor substrate 2 side. Next, a second insulating film layer 10 (“first insulating film” in the claims) is formed on the first insulating film layer 6. The second insulating film layer 10 can be formed of, for example, a silicon oxide film. The film thickness of the second insulating film layer 10 can be set to 200 nm, for example.

  As a second step, a heater opening 10a (a “hole” in the claims) is formed in the second insulating film layer 10 (FIG. 2). The heater opening 10 a is formed so as to penetrate the second insulating film layer 10 and expose the upper surface of the first contact plug 7. The planar shape of the heater opening 10a can be circular when viewed from above. The opening diameter of the upper part of the heater opening 10a can be set to 200 nm, for example.

  As a third step, a heater electrode material 11A is formed (FIG. 3). The heater electrode material 11 </ b> A is formed so as to contact the first contact plug 7, fill the heater opening 10 a, and cover the second insulating film layer 10. For example, titanium nitride can be used as the heater electrode material 11A. The film thickness of the heater electrode material 11A on the second insulating film layer 10 can be set to, for example, 150 nm.

  As the fourth step, the heater electrode 11 (“conductive film plug” in the claims) is formed (FIG. 4). For example, the heater electrode material 11A on the second insulating film layer 10 is removed by polishing using a chemical mechanical polishing (CMP) technique. Thereby, the plug-shaped heater electrode 11 embedded in the heater opening 10a is formed. At this time, it is preferable that the upper surface of the heater electrode 11 and the upper surface of the second insulating film layer 10 are in the same plane.

  As a fifth step, a hard mask 12 (“mask body” in the claims) is formed on the heater electrode 11 (FIG. 5). For example, the hard mask 12 is formed using a lithography technique and an etching technique so as to cover a part of the upper surface of the heater electrode 11 (so that the remaining part is exposed). As the material of the hard mask 12, a material that can act as a mask when the heater electrode 11 is etched is used. For example, when the heater electrode 11 is titanium nitride, a silicon nitride film can be used as the material of the hard mask 12. The area of the upper surface of the hard mask 12 is made smaller than the area of the upper surface of the heater electrode 11 (exposed surface from the second insulating film layer 10). Further, the size of the upper surface of the hard mask 12 is set such that a part of the upper surface of the heater electrode 11 can be left in a predetermined size by the etching process of the heater electrode 11. It is preferable to set the size appropriately according to the etching conditions. The planar shape of the hard mask 12 is not particularly limited, and for example, a circular shape or a rectangular shape can be used. The formation position of the hard mask 12 may be a position that covers a part of the upper surface of the heater electrode 11, and is preferably a central region of the upper surface of the heater electrode 11.

FIG. 6 shows an example of top surface forms of the heater electrode 11 and the hard mask 12. In the example shown in FIG. 6, the hard mask 12 has a circular shape and is formed concentrically with respect to the upper surface of the heater electrode 11. The size of the hard mask 12 (diameter) _{d 2,} when the size of the upper surface of the heater electrode 11 (diameter) _{d 1} is 200 nm, can be, for example, 100 nm. The film thickness of the hard mask 12 can be set to 100 nm, for example.

  As a sixth step, the upper part (part) of the heater electrode 11 is etched using the hard mask 12 as a mask (FIG. 7). The etching conditions are such that a part of the upper surface of the heater electrode 11 under the hard mask 12 can remain. As an etching method, for example, isotropic dry etching can be selected. When the heater electrode 11 is titanium nitride and the heater electrode 11 and the hard mask 12 are in the form as in the above example, for example, etching can be performed under the conditions shown in Table 1 below. Under this condition, the heater electrode 11 can be etched at an etching rate of 5 nm / second. For example, the etching can be performed such that the deepest portion has a depth of 40 nm by etching for 8 seconds.

  As a seventh step, the hard mask 12 is removed (FIG. 8). The hard mask 12 can be removed by, for example, an etching process. When the hard mask 12 is silicon nitride, for example, wet etching using a hot phosphoric acid solution can be used.

FIG. 9 shows an example of the upper surface form of the heater electrode after the etching process. The example shown in FIG. 9 is obtained by etching the form shown in FIG. In FIG. 9, the area | region where the heater electrode 11 was etched is shown by hatching. In the form shown in FIG. 6, when the upper portion of the heater electrode 11 is etched using the hard mask 12 as a mask, the region within the hemisphere of the heater electrode 11 centering on the lower edge of the hard mask 12 from the portion exposed from the hard mask 12. Is etched. That is, the annular region of the upper part of the heater electrode 11 is removed along the outer periphery of the heater opening 10a so as to expose the upper part of the inner wall of the heater opening 10a. As a result, as shown in FIGS. 8 and 9, the heater electrode 11 has a mountain-like shape in which an etched skirt-shaped inclined region 11 c is an inclined surface and a top region 11 b remaining without being etched is an upper surface. A protrusion 11a is formed. The top region 11 b of the protrusion 11 a is formed in a substantially circular shape at the central portion of the heater electrode 11. The inclined region 11c is formed in an annular shape around the top region 11b. Further, the size of the top region 11 b of the protrusion 11 a is smaller than the size of the hard mask 12. For example, in the embodiment shown in FIG. 6 as in the example described above, the diameter _{d 2} is 100nm hard mask 12, the diameter _{d 1} of the upper surface of the heater electrode 11 of the titanium nitride film 200 nm, the etching conditions of Table 1 in 8 seconds when etched, the diameter _{d 3} of the top region 11b of the protrusion 11a may be about 20 nm.

  In the above example, the hard mask 12 having a circular planar shape has been described as an example. However, when the hard mask 12 having a rectangular planar shape is used, the planar shape of the top region 11b of the protrusion 11a It can be a rectangular shape or a rectangular shape close to a rounded corner.

  The “upper surface” in the claims does not include the etched region (inclined region 11 c) of the heater electrode 11.

  5 to 7, the hard mask 12 is formed so as not to cover the second insulating film layer 10, but the hard mask 12 only includes the heater electrode 11 as shown in FIG. 10. You may coat | cover on the 2nd insulating layer 10 not only. In the form shown in FIG. 10, when the heater electrode 11 is etched, the upper part of the heater electrode 11 is shown in FIG. 11 (hatching indicates the region where the heater electrode 11 is etched), as shown in FIG. The protrusion 11a can be formed in contact with the inner wall of the heater opening 10a.

  As an eighth step, a precursor layer 13A of the third insulating film layer is formed on the second insulating film layer 10 and the heater electrode 11 (including the inclined region 11c) (FIG. 12). The precursor layer 13A of the third insulating film layer can be formed as a silicon oxide film, for example. The film thickness of the precursor layer 13A of the third insulating film layer on the second insulating film layer 10 can be set to 150 nm, for example.

As a ninth step, a third insulating film layer 13 (“second insulating film” in the claims) is formed (FIG. 13). For example, by using the CMP technique, the precursor layer 13A of the third insulating film layer is polished and removed so that the second insulating layer 10 and the top region 11b of the protrusion 11a of the heater electrode 11 are exposed, and the protrusion 11a is inclined. The third insulating film layer 13 is formed so as to fill the recess formed by the region 11 c and the second insulating film layer 10. As a result, the inclined region 11 c of the protrusion 11 a is covered with the third insulating film layer 13. The third insulating layer 13 has a circular shape, in its central region, a top region 11b of the circular protrusion 11a of the diameter d ₃ In terms of the above example is about 20nm is exposed.

As a tenth step, the phase change material film 14 is formed so as to cover the second insulating film 10, the top region 11 b of the protrusion 11 a of the heater electrode 11, and the third insulating film 13. An upper electrode 15 is formed on the substrate (FIG. 14). As a material of the phase change material film 14, for example, a chalcogenide material can be used. Examples of the chalcogenide-based material include _binary chalcogenides such as GaSb, InSb, InSe, Sb ₂ Te ₃ and GeTe, ternary chalcogenides such as Ge ₂ Sb ₂ Te ₅ , InSbTe, GaSeTe, SnSb ₂ Te ₄ and InSbGe. Quaternary chalcogenides such as AgInSbTe, (GeSn) SbTe, GeSb (SeTe), and Te ₈₁ Ge ₁₅ Sb ₂ S ₂ can be used. The film thickness of the phase change material film 14 can be set to 100 nm, for example. Further, as a material of the upper electrode 15, for example, titanium nitride can be used. The film thickness of the upper electrode 15 can be set to, for example, 50 nm.

  The semiconductor device 1 can be manufactured by the manufacturing method including the above steps. In the semiconductor device 1 manufactured by the manufacturing method of the present invention, the area of the heater electrode 11 in contact with the phase change material film 14 can be made smaller than the minimum area of the heater electrode 11 that can be formed using lithography technology. . Further, by appropriately setting the form of the hard mask 12 and the etching conditions, the contact area between the phase change material film 14 and the heater electrode 11 can be controlled to an arbitrary size. Thereby, the heat generation efficiency of the phase change material film 14 can be improved.

  A method for manufacturing a semiconductor device according to Example 2 of the present invention will be described. 15 to 17 are schematic views for explaining a method for manufacturing a semiconductor device according to the second embodiment of the present invention. 16 is a schematic partial plan view of the semiconductor device shown in FIG. 15 to 17, the same elements as those in the first embodiment are denoted by the same reference numerals. In the first embodiment and the second embodiment, the form of the hard mask used is different.

  In the manufacturing method according to the second embodiment, the first to fourth steps are the same as the first to fourth steps of the first embodiment.

  As a fifth step, a hard mask 22 is formed so as to cover a part of the upper surface of the heater electrode 11 and the upper surface of the second insulating film layer 10 (FIG. 15). In the example shown in FIGS. 5 to 7 in Example 1, the hard mask is formed only in the region covering the heater electrode, but in this embodiment, the hard mask 22 etches the heater electrode 11. The region is formed to have a through hole 22d. For example, in the example shown in FIGS. 15 and 16, the hard mask 22 has a covering portion 22 a that covers a part of the upper surface of the heater electrode 11 in order to form a protrusion 11 a having a top region on the heater electrode 11. A support portion 22c that covers the second insulating film layer 10 to support the covering portion 22a, and a bridging portion 22b that bridges the covering portion 22a and the support portion 22c to support the covering portion 22a on the support portion 22c. And having. The through hole 22d is formed so as to be surrounded by the covering portion 22a, the bridging portion 22b, and the support portion 22c.

The form regarding the coating | coated part 22a of the hard mask 22 can be made into the form similar to the form of the hard mask in Example 1. FIG. In the form shown in FIG. 16, the bridging portion 22b is formed at two places for one covering portion 22a, but it may be at one place. In addition, the bridging portion 22b can be formed at three or more locations on one covering portion 22a. In this case, the through-hole 22d is formed at the location where the bridging portion 22b is formed, and the heater electrode 11 is etched later. The position is such that the protrusion 11a can be formed on the heater electrode 11 by processing. Further, it is preferable that the width w of the bridging portion 22b is set so that the covering portion 22a does not peel off from the heater electrode 11 even when a large force is applied to the hard mask 22 by a cleaning process or the like. Further, if the width w of the bridging portion 22b is too large, the upper surface of the heater electrode 11 other than the predetermined region may remain, so that the width of the bridging portion 22b does not hinder the formation of the protrusion 11a. The size and position of the through hole 22d are set such that the heater electrode does not remain on the outer peripheral portion of the upper surface of the heater electrode 11. For example, if the upper surface of the diameter of the heater electrode 11 is 200nm in the same manner for example as in Example 1, the size of the circular cover portion 22a (corresponding to the diameter) _{d 5} may be, for example 100 nm. The width w of the bridging portion 22b can be set to 40 nm, for example. For one heating electrode 11, size combined two through holes 22 d d _4, the size of the upper surface of the heater electrode 11 and when the equal or preferable.

  The hard mask 22 can be formed using the lithography technique and the etching technique in the same manner as in the first embodiment. The covering portion 22a, the bridging portion 22b, and the support portion 22c in the hard mask 22 can be integrally formed. The hard mask 22 can be formed as a silicon nitride film, for example. The film thickness of the hard mask 22 can be set to 100 nm, for example. In the form shown in FIG. 16, the support portion 22c is formed on the entire upper surface of the second insulating film layer 10. However, if the strength and area can support the covering portion 22a, the second insulating film It can also be partially formed on the upper surface of the layer 10. Further, the hard mask 22 may be formed so as to act as a mask for the plurality of heater electrodes 11.

  As a sixth step, the upper part (part) of the heater electrode 11 is etched using the hard mask 22 as a mask (FIG. 17). The etching conditions are such that a part of the upper surface of the heater electrode 11 under the hard mask 22 can remain. That is, like the first embodiment, the upper portion of the heater electrode 11 is etched so that the protrusion 11a can be formed on the upper portion of the heater electrode 11. As an etching method, for example, isotropic dry etching can be selected. When the heater electrode 11 is titanium nitride and the heater electrode 11 and the hard mask 22 are in the form as in the above example, the etching can be performed under the conditions shown in Table 1 of Example 1. Under this condition, the heater electrode 11 can be etched at an etching rate of 5 nm / second. For example, the etching can be performed at a depth of 40 nm at the deepest portion by etching for 8 seconds. In this case, the heater electrode 11 portion under the bridging portion 22b can also be removed by etching, and the inclined region of the protruding portion 11a can be obtained. Thereby, the shape of the heater electrode 11 can be made into the shape similar to the shape of the heater electrode 11 in Example 1. FIG.

  In the manufacturing method according to the second embodiment, the seventh process to the tenth process can be the same as the seventh process to the tenth process of the first embodiment.

  According to the present embodiment, the hard mask 22 portion (covering portion 22a) for forming the protruding portion 11a is connected to the support portion 22c by the bridging portion 22b, so that the covering portion 22a on the upper surface of the heater electrode 11 is provided. Contact strength can be increased. For example, in Example 1, after etching the upper portion of the heater electrode, the hard mask is supported only by the top region of the protrusion of the heater electrode (FIG. 7). In this case, there is a concern that the hard mask may be peeled off when a strong force is applied. Therefore, it becomes difficult to carry out a cleaning process or the like in which a large mechanical force is applied. On the other hand, according to the second embodiment, since the covering portion 22a of the hard mask 22 is not likely to be peeled off from the upper portion of the heater electrode 11, a cleaning process or the like can be performed.

  The form of the hard mask illustrated in Example 1 and Example 2 is an example, and the form of the hard mask is not limited to these, and the area of the heater electrode in contact with the phase change material layer can be reduced. Any form can be used.

  The upper form of the heater electrode after the etching process illustrated in the first embodiment and the second embodiment is an example, and is not limited thereto, as long as the area of the heater electrode in contact with the phase change material layer can be reduced. Either form can be used.

  The method for manufacturing a semiconductor device of the present invention has been described based on the above embodiment, but is not limited to the above embodiment, and is within the scope of the present invention and based on the basic technical idea of the present invention. It goes without saying that various modifications, changes and improvements can be included in the above embodiment. Further, various combinations, substitutions, or selections of various disclosed elements are possible within the scope of the claims of the present invention.

  Further problems, objects, and developments of the present invention will become apparent from the entire disclosure of the present invention including the claims.

DESCRIPTION OF SYMBOLS 1 Semiconductor device 2 Semiconductor substrate 3 1st diffused layer 4 2nd diffused layer 5 Gate electrode 6 1st insulating film layer 7 1st contact plug 8 2nd contact plug 9 Power supply wiring 10 2nd insulating film layer 10a Heater opening part 11 Heater Electrode 11a Protruding portion 11b Top region 11c Inclined region 11A Heater electrode material 12 Hard mask 13 Third insulating film layer 13A Precursor layer of third insulating film 14 Phase change material film 15 Upper electrode 22 Hard mask 22a Covering portion 22b Crosslinking portion 22c Support part 22d Through hole

Claims (9)

Forming a hole in the first insulating film;
Forming a conductive film plug in the hole;
Forming a mask body on the upper surface of the conductive film plug so that a part of the upper surface of the conductive film plug is exposed;
Selectively etching the conductive film plug using the mask body as a mask to reduce the area of the upper surface of the conductive film plug;
Forming a phase change material layer in contact with the reduced upper surface;
A method for manufacturing a semiconductor device, comprising: Forming a hole in the first insulating film;
Forming a conductive film plug in the hole;
Forming a mask body on the upper surface of the conductive film plug so that a part of the upper surface of the conductive film plug is exposed;
Selectively etching the conductive film plug using the mask body as a mask to form a protrusion on the conductive film plug; and
Forming a phase change material layer in contact with the top region of the protrusion;
A method for manufacturing a semiconductor device, comprising: Forming a hole in the first insulating film;
Forming a conductive film plug in the hole;
Forming a mask body on the upper surface of the conductive film plug so as to cover a part of the upper surface of the conductive film plug;
Selectively etching part of the upper portion of the conductive film plug using the mask body as a mask;
Forming a phase change material layer so as to be in contact with at least a part of the upper surface of the conductive film plug covered with the mask body;
A method for manufacturing a semiconductor device, comprising: In the step of etching the conductive film plug,
4. The semiconductor device according to claim 1, wherein the conductive film plug is subjected to an isotropic etching process, and a hemispherical region is removed around a lower edge of the mask body. Manufacturing method. In the step of etching the conductive film plug,
The conductive film plug is subjected to an isotropic etching process, and an annular or arcuate region is removed along an outer periphery of the opening of the hole. A method for manufacturing a semiconductor device.   6. The method according to claim 1, further comprising a step of embedding a second insulating film in a portion where the conductive film plug is etched before the step of forming the phase change material layer. Semiconductor device manufacturing method. In the step of forming the mask body,
The area of the mask body plane is made smaller than the area of the upper surface of the conductive film plug, and the mask body is formed so as to be concentric with the hole. The manufacturing method of the semiconductor device as described in any one of these. In the step of forming the mask body,
The mask body is formed on the conductive film plug and the first insulating film so as to have a through hole exposing a part of the upper surface of the conductive film plug. A manufacturing method of a semiconductor device given in any 1 paragraph.   The through hole is formed by a covering portion that covers a part of the upper surface of the conductive film plug, a support portion that covers the first insulating film, and a bridging portion that connects the covering portion and the support portion. The method of manufacturing a semiconductor device according to claim 8.

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