Semiconductor nonvolatile storage element and method of fabricating the same

Abstract

To provide a semiconductor nonvolatile storage device capable of applying distributed voltage efficiently to a ferroelectric capacitor in a semiconductor nonvolatile storage device having an MFMIS structure without enlarging a memory cell area and a method of fabricating the same, a ferroelectric nonvolatile storage element is constructed by a structure successively laminated with a first insulator layer ( 3 ), a first conductor layer ( 4 ), a ferroelectric layer ( 5 ) and a second conductor layer ( 6 ) on a channel region and is constructed by a structure having a third conductor ( 9 ) and a fourth conductor ( 10 ) respectively laminated on a source region and a drain region, in which the third conductor ( 9 ) and the fourth conductor ( 10 ) are opposed to each other via the first conductor layer ( 4 ) and a second insulator thin film ( 11 ).

1 - 12 . (Canceled)  
     
     
         13 . A semiconductor nonvolatile storage element, which is a ferroelectric nonvolatile storage element comprising: 
 a semiconductor substrate defining a source region, a drain region and a channel region between the source region and the drain region;    a first insulator layer extending over the entire channel region, a first conductor layer formed on the first insulator layer, a ferroelectric layer formed on the first conductor and a second conductor layer formed on the ferroelectric layer, such that the channel region, the first insulator and the first conductor layer forms a first capacitor which has an electrostatic capacitance C 1 , and the ferroelectric layer forms a second capacitor which has an electrostatic capacitor C 2 ;    a third conductor layer formed on the source region, and a second insulator thin film between the third conductor layer and the first conductor layer, such that the third conductor layer, the second insulator and the first conductor layer forms a third capacitor which has an electrostatic capacitance C 3 ; and    a fourth conductor layer formed on the drain region, and a third insulator thin film between the fourth conductor layer and the first conductor layer such that the fourth conductor layer, the third insulator and the first conductor layer forms a fourth capacitor which has an electrostatic capacitance C 4 ,    wherein a coupling ratio (CI/(CI+C 2 )) of the C 2  capacitance to the composite electrostatic capacitance CI (CI=C 1 +C 3 +C 4 ) is set such that distributed voltage is effectively applied to the capacitor C 2  of the ferroelectric layer.    
     
     
         14 . The semiconductor nonvolatile storage element according to  claim 13 , wherein the semiconductor substrate is an SOI substrate.  
     
     
         15 . The semiconductor nonvolatile storage element according to any one of  claim 13 , wherein an area of the second conductor layer above the ferroelectric layer is smaller than an area of the ferroelectric layer.  
     
     
         16 . The semiconductor nonvolatile storage element according to any one of  claim 13 , wherein the second conductor layer is disposed above an element isolating region of the semiconductor substrate.  
     
     
         17 . The semiconductor nonvolatile storage element according to any one of  claim 13 , wherein each of the first insulator layer and the second insulator thin film comprises a layer of one material or a layer laminated with two or more of materials selected from a group consisting of SiO 2 (silicon oxide), SiN(silicon nitride), SiON(silicon oxynitride), SiO 2 —SiN(ON film: silicon oxide-silicon nitride), SiO 2 —SiN—SiO 2 (ONO film: silicon oxide-silicon nitride silicon oxide), Ta 2 O 5 , SrTiO 3 , TiO 2 , (Ba, Sr)TiO 3 , Al 2 O 3 , ZrO 2 , HfO 2 , Y 2 O 3 , CeO 2 , CeZrO 2  and YSZ(yttrium oxide stabilized zirconium oxide).  
     
     
         18 . The semiconductor nonvolatile storage element according to any one of  claim 13 , wherein the ferroelectric layer is a layer of one material selected from a group consisting of SrBi 2 Ta 2 O 9 , PbTio 3 , PbZr x Ti 1-x O 3 , Pb y La 1-y Zr x Ti 1-x O 3 , Bi 4 Ti 3 O 12 , SrNbO 7 , Pb 5 Ge 3 O 11  and Sr 2 Ta x Nb 1     —     x O 7 .  
     
     
         19 . The new semiconductor nonvolatile storage element according to  claim 13 , wherein the first insulator layer and the second insulator thin film form a U-shaped insulator.  
     
     
         20 . The semiconductor nonvolatile storage element according to  claim 19 , wherein a total effective area of an MIS structure formed by the semiconductor substrate, the first insulator layer and the first conductor layer and of an MIM structure formed by side walls of the third and fourth conductor and side walls of the second insulator thin film is adjustable by controlling a height of the first conductor layer and the third and fourth conductors.