Semiconductor devices having silicided electrodes

Abstract

The invention relates to a method for fabricating a semiconductor device having a semiconductor body that comprises a first semiconductor structure having a dielectric layer and a first conductor, and a second semiconductor structure having a dielectric layer and a second conductor, that part of the first conductor which adjoins the dielectric layer having a work function different from the work function of the corresponding part of the second conductor. In one embodiment of the invention, after the dielectric layer has been applied to the semiconductor body, a metal layer is applied to the said dielectric layer, and then a silicon layer is deposited on the metal layer and is brought into reaction with the metal layer at the location of the first semiconductor structure, forming a metal silicide. In one embodiment, those parts of the conductors which have different work functions are formed by etching a layer other than the silicon layer, in particular a metal layer, at the location of one of the two semiconductor structures. Furthermore, a further metal layer is applied over the silicon layer and is used to form a further metal silicide at the location of the second transistor. One embodiment of the invention is particularly suitable for use in CMOS technology and results in both PMOS and NMOS transistors with favourable properties.

1 . A semiconductor device, comprising: 
 a first semiconductor structure having a dielectric layer and a first gate electrode, wherein the first gate electrode comprises a first conductor;    a second semiconductor structure having a dielectric layer and a second gate electrode, wherein the second gate electrode comprises a second conductor which differs from the first conductor, wherein a part of the second conductor that adjoins the dielectric layer has a different work function from a corresponding part of the first conductor, and wherein the semiconductor device is fabricated by a method, which comprises: 
 forming a first metal layer on at least one of the dielectric layers; and  
 depositing a silicon layer on the first metal layer, wherein the silicon layer and the first metal layer react with each other at least one of the semiconductor structures so as to form a first metal silicide.  
   
     
     
         2 . The semiconductor device according to  claim 1 , wherein the first and second gate electrodes have substantially the same thickness.  
     
     
         3 . The semiconductor device according to  claim 1 , wherein at least one of the semiconductor structures is a field-effect transistor.  
     
     
         4 . The semiconductor device according to  claim 1 , wherein the parts of the conductors having different work functions are formed by etching a layer other than the silicon layer at one of the semiconductor structures.  
     
     
         5 . The semiconductor device according to  claim 4 , wherein the etching of the layer other than the silicon layer is etching the first metal layer.  
     
     
         6 . The semiconductor device according to  claim 1 , wherein the first metal layer is formed from a metal selected from the group consisting of nickel, titanium and cobalt.  
     
     
         7 . The semiconductor device according to  claim 1 , wherein the method further comprises, after the first and second semiconductor structures have been formed, depositing a second metal layer, the second metal layer being a siliciding metal layer, wherein a further metal silicide is formed at least one of the first and second semiconductor structures.  
     
     
         8 . The semiconductor device according to  claim 7 , wherein the second metal silicide comprises a silicon content different from the silicon content of the first metal silicide.  
     
     
         9 . The semiconductor device according to  claim 7 , wherein the second metal layer is formed from a metal selected from the group consisting of nickel, titanium and cobalt.  
     
     
         10 . The semiconductor device according to  claim 1 , wherein the silicide layer is formed from a disilicide.  
     
     
         11 . The semiconductor device according to  claim 1 , further comprising a second metal layer between the first metal layer and one of the dielectrics, the second metal layer being a non-siliciding metal layer.  
     
     
         12 . A semiconductor device, comprising: 
 a first semiconductor structure having a dielectric layer and a first gate electrode, wherein the first gate electrode comprises a first conductor formed from a first metal silicide; and    a second semiconductor structure having a dielectric layer and a second gate electrode,    wherein the second gate electrode comprises a second conductor which differs from the first conductor, wherein the second conductor includes a second metal silicide which is different from the first metal silicide, and wherein a part of the second conductor that adjoins the dielectric layer has a different work function from a corresponding part of the first conductor.    
     
     
         13 . The semiconductor device according to  claim 12 , wherein the first and second gate electrodes have substantially the same thickness.  
     
     
         14 . The semiconductor device according to  claim 12 , wherein at least one of the semiconductor structures is a field-effect transistor.  
     
     
         15 . The semiconductor device according to  claim 12 , wherein the first metal silicide is a disilicide, and the second metal silicide is a monosilicide.  
     
     
         16 . The semiconductor device according to  claim 12 , wherein the parts of the conductors having different work functions are formed by etching a layer other than the silicon layer at one of the semiconductor structures.  
     
     
         17 . The semiconductor device according to  claim 16 , wherein the etching of the layer other than the silicon layer is etching the first metal layer.  
     
     
         18 . The semiconductor device according to  claim 12 , wherein the first metal layer is formed from a metal selected from the group consisting of nickel, titanium and cobalt.  
     
     
         19 . The semiconductor device according to  claim 12 , further comprising a second metal layer, the second metal layer comprising a siliciding metal layer, wherein a further metal silicide is formed at least one of the semiconductor structures.  
     
     
         20 . The semiconductor device according to  claim 19 , wherein the second metal layer is formed from a metal selected from the group consisting of nickel, titanium and cobalt.  
     
     
         21 . The semiconductor device according to  claim 19 , wherein the second metal silicide has a silicon content different from the silicon content of the first metal silicide.  
     
     
         22 . The semiconductor device according to  claim 12 , further comprising a second metal layer formed between the first metal layer and one of the dielectrics, the second metal layer being a non-siliciding metal layer.