Method for fabricating semiconductor storage device

Abstract

The semiconductor storage device comprises memory cell transistors formed on a semiconductor substrate 10 ; first insulation films 42 covering the top surfaces and the side surfaces of gate electrodes 20 of the memory cell transistors; through-holes 40 opened on first diffused layers 24 ; a second insulation film 36 with through-holes 40 opened on second diffused layers 26 formed in; capacitors formed on the inside walls and the bottoms of the through-holes 40 and including capacitor storage electrodes 46 , connected to the first diffused layers 24 ; capacitor dielectric films 48 covering the capacitor storage electrodes 46 , and capacitor-opposed electrodes 54 covering at least a part of the capacitor dielectric films 48 ; and, contact conducting films 44 formed on the inside walls and bottoms of the through-holes 38 , and connected to the second diffused layers. This structure of the semiconductor storage device makes it unnecessary to secure an alignment allowance for alignment of the through-holes 40 opened on the second diffused layer 26 with the gate electrode 20 , which permits the semiconductor storage device to have a small memory cell area.

1 . A method for fabricating a semiconductor device comprising the steps of: 
 forming a first conductor pattern over a semiconductor substrate;    forming a first insulation film covering the first conductor pattern;    forming over the first insulation film a second insulation film having etching characteristics different from those of the first insulation film;    polishing the second insulation film;    forming over the second insulation film a third insulation film having etching characteristics different from those of the second insulation film;    forming over the third insulation film a fourth insulation film having etching characteristics different from those of the third insulation film;    forming a hole in the fourth insulation film, the third insulation film, the second insulation film and the first insulation film; and    forming a second conductor in the hole,    the step of forming the hole including a first step of etching the fourth insulation film, a second step of etching the third insulation film, a third step of etching the second insulation film, and a fourth step of etching the first insulation film, an etching condition at the first step being different from that at the second step.    
     
     
         2 . A method for fabricating the semiconductor device according to  claim 1 , wherein 
 in the step of polishing the second insulation film, the second insulation film is polished by chemical mechanical polishing.    
     
     
         3 . A method for fabricating the semiconductor device according to  claim 1 , wherein 
 each of the first insulation film and the third insulation film is formed of silicon nitride, and    each of the second insulation film and the fourth insulation film is formed of non-doped silicon oxide.    
     
     
         4 . A method for fabricating a semiconductor device comprising the steps of: 
 forming a first conductor over a semiconductor substrate;    forming a first insulation film covering the first conductor;    forming over the first insulation film a second insulation film having etching characteristics different from those of the first insulation film;    polishing the second insulation film;    forming over the second insulation film a third insulation film;    forming over the third insulation film a fourth insulation film;    forming a hole exposing a second conductor in the fourth insulation film, the third insulation film and the second insulation film; and    forming a third conductor in the hole,    the step of forming the hole including a first step of etching the fourth insulation film, a second step of etching the third insulation film and a third step of etching the second insulation film, an etching condition at the first step being different from that at the second step.    
     
     
         5 . A method for fabricating the semiconductor device according to  claim 4 , wherein 
 in the step of polishing the second insulation film, the second insulation film is polished by chemical mechanical polishing.    
     
     
         6 . A method for fabricating the semiconductor device according to  claim 4 , wherein 
 each of the first insulation film and the third insulation film is formed of silicon nitride, and    each of the second insulation film and the fourth insulation film is formed of non-doped silicon oxide.    
     
     
         7 . A method for fabricating a semiconductor device comprising the steps of: 
 forming an impurity doped region in a semiconductor substrate;    forming a first conductor over the semiconductor substrate;    forming a first insulation film covering the first conductor;    forming over the first insulation film a second insulation film having etching characteristics different from those of the first insulation film;    polishing the second insulation film;    forming over the second insulation film a third insulation film;    forming over the third insulation film a fourth insulation film;    forming a hole exposing the impurity doped region in the fourth insulation film, the third insulation film and the second insulation film; and    forming a second conductor in the hole,    the step of forming the hole including a first step of etching the fourth insulation film, a second step of etching the third insulation film and a third step of etching the second insulation film, an etching condition at the first step being different from that at the second step.    
     
     
         8 . A method for fabricating the semiconductor device according to  claim 7 , wherein 
 in the step of polishing the second insulation film, the second insulation film is polished by chemical mechanical polishing.    
     
     
         9 . A method for fabricating the semiconductor device according to  claim 7 , wherein 
 each of the first insulation film and the third insulation film is formed of silicon nitride, and    each of the second insulation film and the fourth insulation film is formed of non-doped silicon oxide.    
     
     
         10 . A method for fabricating the semiconductor device according to  claim 1 , wherein 
 in the step of forming the hole, an etching rate of the second insulation film at the first step is lower than an etching rate of the third insulation film at the first step and an etching rate of the second insulation film at the second step.    
     
     
         11 . A method for fabricating the semiconductor device according to  claim 4 , wherein 
 in the step of forming the hole, an etching rate of the third insulation film at the first step is lower than an etching rate of the fourth insulation film at the first step and an etching rate of the third insulation film at the second step.    
     
     
         12 . A method for fabricating the semiconductor device according to  claim 7 , wherein 
 in the step of forming the hole, an etching rate of the third insulation film at the first step is lower than an etching rate of the fourth insulation film at the first step and an etching rate of the third insulation film at the second step.    
     
     
         13 . A method for fabricating a semiconductor device according to  claim 1 , wherein the first insulation film comprises silicon oxide.  
     
     
         14 . A method for fabricating a semiconductor device according to  claim 1 , wherein the second insulation film comprises silicon nitride.  
     
     
         15 . A method for fabricating a semiconductor device according to  claim 1 , wherein the third insulation film comprises silicon oxide.  
     
     
         16 . A method for fabricating a semiconductor device according to  claim 1 , further comprising steps of forming capacitors, bit lines and wiring layers to constitute a memory device.  
     
     
         17 . A method for fabricating a semiconductor device according to  claim 4 , wherein the first insulation film comprises silicon oxide.  
     
     
         18 . A method for fabricating a semiconductor device according to  claim 4 , wherein the second insulation film comprises silicon nitride.  
     
     
         19 . A method for fabricating a semiconductor device according to  claim 4 , wherein the third insulation film comprises silicon oxide.  
     
     
         20 . A method for fabricating a semiconductor device according to  claim 4 , further comprising steps of forming capacitors, bit lines and wiring layers to constitute a memory device.  
     
     
         21 . A method for fabricating the semiconductor device according to  claim 7 , wherein 
 in the step of forming the hole, an etching rate of the third insulation film at the first step is lower than an etching rate of the fourth insulation film at the first step and an etching rate of the third insulation film at the second step.    
     
     
         22 . A method for fabricating the semiconductor device according to  claim 7 , wherein 
 in the step of forming the hole, an etching rate of the third insulation film at the first step is lower than an etching rate of the fourth insulation film at the first step and an etching rate of the third insulation film at the second step.    
     
     
         23 . A method for fabricating a semiconductor device according to  claim 7 , wherein the first insulation film comprises silicon oxide.  
     
     
         24 . A method for fabricating a semiconductor device according to  claim 7 , wherein the second insulation film comprises silicon nitride.