Abstract:
This invention relates to a method for forming a stacked capacitor in a semiconductor device. This invention can increase the capacitance of a capacitor by planarizing a polysilicon layer for a charge storage electrode and forming a recess on the planarized polysilicon layer.

Description:
FIELD OF THE INVENTION 
     This invention relates to a method for forming a stacked capacitor in a semiconductor device, and more particularly, to a method for increasing the capacitance of a capacitor by planarizing a polysilicon layer for a charge storage electrode and forming a recess on the planarized polysilicon layer. 
     BACKGROUND 
     Generally, as the semiconductor device becomes more integrated, the effective area of the capacitor must be decreased. Therefore, the capacitor must be manufactured with a larger capacitance in a limited effective area. 
     Therefore, it is the object of the present invention to provide a method for forming a stacked capacitor in a semiconductor device which can increase the memory capacity in a semiconductor device as the capacitance of the capacitor in the limited effective area of the capacitor increases. 
     SUMMARY OF THE INVENTION 
     To achieve the above object and other advantages, in the present invention, a field oxide layer is formed on a silicon substrate. A gate oxide layer, a gate electrode layer and an insulating layer are sequentially formed on the silicon substrate. The gate oxide layer, the gate electrode, layer and the insulating layer are etched to form a gate electrode. An impurity region is formed on the silicon substrate. An oxide spacer is formed on the side wall of the gate electrode. A first oxide layer, a nitride layer and a second oxide layer are formed on the silicon substrate including on the gate electrode and the oxide spacer. A portion of the first oxide layer, nitride layer and second oxide layer are etched using a first mask so as to expose the impurity region, thereby forming a contact hole. A first polysilicon layer is deposited on the second oxide layer and the contact hole. The first polysilicon layer is then planarized. A portion of the first polysilicon layer is etched using a second mask to depth that does not expose the second oxide layer. A third oxide layer and a photoresist are sequentially formed on the first polysilicon layer, and then the photoresist is patterned to expose portions of the third oxide layer. The third oxide layer and the first polysilicon layer are sequentially etched to expose both side portions of the second oxide layer, thereby forming multiple recesses on the center of the first polysilicon layer and on the second oxide layer. The photoresist is then removed. A second polysilicon layer is deposited on the third oxide layer including on the recesses. The second polysilicon layer is etched to form a polysilicon spacer on each inner wall of the recesses. The third oxide layer and the second oxide layer are removed, thereby forming a charge storage electrode. A capacitor dielectric layer is formed on the surface of the charge storage electrode. A plate electrode is formed on the surface of the capacitor dielectric layer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described with reference to the attached drawings, in which: 
     FIGS. 1A to 1F illustrate the sequential fabrication process for forming a stacked capacitor in a semiconductor device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1A, a field oxide layer 2 is formed on a silicon substrate. A gate oxide layer 3, a gate electrode layer 4 and an insulating layer 7 are sequentially formed on the silicon substrate 1. The gate oxide layer 3, the gate electrode layer 4 and the insulating layer 7 are etched to form a gate electrode 4A. An impurity region 5 for a source or drain electrode is formed on the silicon substrate 1. An oxide spacer 6 is formed on the side wall of the gate electrode 4A. A first oxide layer 8, a nitride layer 9 and a second oxide layer 10 are sequentially formed on the silicon substrate 1 including on the gate electrode 4A and the oxide spacer 6. A portion of the first oxide layer 8, nitride layer 9 and second oxide layer 10 is etched using a first mask (not shown), thereby forming a contact hole 17. 
     Referring to FIG. 1B, a first polysilicon layer 11 is deposited and planarized on the second oxide layer 10 and the contact hole 17. 
     Referring to FIG. 1C, a portion of the first polysilicon layer 11 is etched using a second mask (not shown) to a depth that does not expose the second oxide layer 10. The second mask forms a pattern inverse of the pattern formed by the first mask. 
     Referring to FIG. 1D, a third oxide layer 12 and a photoresist 13 are sequentially formed on the first polysilicon layer 11. The photoresist 13 is patterned to expose portions of the third oxide layer 12. The third oxide layer 12 and the first polysilicon layer 11 exposed by the patterned photoresist 13 are sequentially etched by employing a dry-etching process to expose both side portions of the second oxide layer 10, thereby forming numerous recesses 18 on the center of the first polysilicon layer 11 and on both sides of the second oxide layer 10. 
     Referring to FIG. 1E, the photoresist 13 is removed. Then, a second polysilicon layer 14 is deposited on the third oxide layer 12 including on the recesses 18. The second polysilicon layer 14 is anisotropically etched by an anisotropic etching process to form a polysilicon spacer 14a on each inner wall of the recesses 18. 
     Referring to FIG. 1F, the third oxide layer 12 and the second oxide layer 10 are removed by means of a wet-etching process, thereby forming a charge storage electrode 19 which is comprised of the first polysilicon layer 11 and the polysilicon spacer 14a. A capacitor dielectric layer 15 is formed on the surface of the charge storage electrode 19. A plate electrode 20 is formed on the surface of the capacitor dielectric layer 15. The nitride layer 9 is used as an etching barrier during the wet-etching process. 
     As described above, according to the present invention, the capacitor increases the memory capacity in a semiconductor device by increasing the capacitance of a capacitor. 
     Although this invention has been described in its preferred embodiment with a certain degree of particularity, one skilled in the art should know that the preferred embodiment disclosed herein is only an example and that the construction, combination and arrangement of its parts may be varied without departing from the spirit and scope of the present invention.