Semiconductor intergrated circuit device and process for producing the same

Abstract

A semiconductor integrated circuit device with third gates comprising second conduction type source/drain diffusion layer regions 205 formed first conduction type well 201, floating gates 203 b formed on semiconductor substrate 200 through an insulator film 202, control gates 211 a formed on floating gates 203 b through nitrogen-introduced silicon oxide film 210 a and third gates 207 a different from the floating gates and the control gates, formed through the semiconductor substrates, the floating gates, the control gates and the insulator film, where the third gates are formed as filled in gaps between the floating gates existing in a vertical direction to word lines and channels and the height of third gates 207 a thus formed is made lower than that of floating gates 203 b, has improved reduction of memory cell size and operating speed and improved reliability after programming/erasing cycles.

1 - 17 . (canceled)  
   
   
       18 . A process for producing a nonvolatile semiconductor memory device, which comprises the steps of: 
 forming a first conductive film having a region in which a height of a middle portion of a top surface of the first conductive film is lower than that of two sides of the top surface of the first conductive film, and extending in a first direction over a substrate;    forming an insulator film on the conductive film;    forming a second conductive film on the insulator film;    patterning the second conductive film such that the second conductive film extends in a second direction which crosses the first direction.    
   
   
       19 . A process for producing a nonvolatile semiconductor memory device according to  claim 18 , wherein the first conductive film has a U-shape in a section of the second direction.  
   
   
       20 . A process for producing a nonvolatile semiconductor memory device according to  claim 18 , wherein the first conductive film is a lamination film.  
   
   
       21 . A process for producing a nonvolatile semiconductor memory device according to  claim 18 , wherein the step of forming the first conductive film comprises steps of forming a conductive film over the substrate and forming a further conductive film on the conductive film formed over the substrate, and etching the further conductive film by anisotropic dry etching.  
   
   
       22 . A process according to  claim 18 , wherein the first conductive film is a floating gate and the second conductive film is a word line.  
   
   
       23 . A process for producing a nonvolatile semiconductor memory device, which comprises the steps of: 
 forming first patterns on a substrate;    forming a second pattern having a region in which a height of a middle portion of a top surface of the second pattern is lower than that of two sides of the top surface of the second pattern to act as floating gates in gaps formed between the first patterns; and    forming control gates above the floating gates.    
   
   
       24 . A process for producing a nonvolatile semiconductor memory device according to  claim 23 , wherein the second pattern has a U-shape in a section of a direction in which the control gates extend.  
   
   
       25 . A process for producing a nonvolatile semiconductor memory device according to  claim 23 , wherein the first patterns are formed by any one of the following methods: 
 a first method including forming a polysilicon film to completely fill the gaps, and dry etching the polysilicon film;    a second method including forming a polysilicon film to completely fill the gaps, and polishing the polysilicon film by chemical mechanical polishing, followed by dry etching;    a third method including forming a polysilicon film so as not to completely fill the gaps, and polishing the polysilicon film by chemical mechanical polishing;    a fourth method including forming a polysilicon film so as not to completely fill the gaps, forming an organic film to fill the gaps, and dry etching the organic film and the polysilicon film; and    a fifth method including forming a polysilicon film so as not to completely fill the gaps, depositing a silicon oxide film to fill the gaps, and polishing the silicon oxide film and the polysilicon film by chemical mechanical polishing.    
   
   
       26 . A process for producing a nonvolatile semiconductor memory device, which comprises the step of: 
 forming patterns extending in a first direction on a substrate;    forming a first conductive film on top of the patterns, on sides of the patterns, and over the substrate so as not to completely fill gaps between the patterns;    removing the first conductive film on the top of the patterns;    forming an insulator film on the first conductive film;    forming a second conductive film on the insulator film; and    patterning the second conductive film such that the second conductive film extends in a second direction crossing the first direction.    
   
   
       27 . A process for producing a nonvolatile semiconductor memory device according to  claim 26 , wherein the first conductive film has a U-shape in a section of the second direction.  
   
   
       28 . A process for producing a nonvolatile semiconductor memory device according to  claim 26 , wherein the step of removing is conducted by chemical mechanical polishing.  
   
   
       29 . A process for producing a nonvolatile semiconductor memory device according to  claim 26 , the patterns are made of an insulator.  
   
   
       30 . A process for producing a nonvolatile semiconductor memory device according to  claim 26 , wherein the first conductive film is a floating gate and the second conductive film is a word line.