Method for forming wiring, semiconductor device, and method for manufacturing semiconductor device

Abstract

A wiring which is formed using a conductive film containing copper and whose shape is controlled is provided. A transistor including an electrode which is formed in the same layer as the wiring is provided. Further, a semiconductor device including the transistor and the wiring is provided. A resist mask is formed over a second conductive film stacked over a first conductive film; part of the second conductive film and part of the first conductive film are removed with use of the resist mask as a mask so that the first conductive film has a taper angle greater than or equal to 15° and less than or equal to 45′; and the resist mask is removed. The first conductive film contains copper.

What is claimed is: 
     
         1 . A method for manufacturing a semiconductor device, comprising the steps of:
 forming a gate electrode by a method comprising the steps of:
 forming a first conductive film comprising copper over a substrate; 
 forming a second conductive film comprising at least one of tungsten, cobalt, nickel, tin, and molybdenum over the first conductive film; 
 forming a resist mask over the second conductive film; 
 removing a part of the second conductive film and a part of the first conductive film with use of the resist mask as a mask so that the first conductive film has a taper angle greater than or equal to 15° and less than or equal to 45° and the second conductive film has a region which is not in contact with the first conductive film; and 
 removing the resist mask; 
   forming a gate insulating film over the gate electrode;   forming a semiconductor film overlapping with the gate electrode with the gate insulating film therebetween; and   forming a pair of electrodes in contact with the semiconductor film.   
     
     
         2 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein a region of the first conductive film which is in contact with the second conductive film is etched more rapidly than other region of the first conductive film which is not in contact with the second conductive film.   
     
     
         3 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein an insulating film is provided under the first conductive film, and   wherein the insulating film comprises one of silicon nitride, silicon nitride oxide, aluminum nitride and aluminum oxide.   
     
     
         4 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein the semiconductor film comprises an oxide semiconductor.   
     
     
         5 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein the gate insulating film comprises a silicon nitride or a silicon oxynitride.   
     
     
         6 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein the second conductive film is removed after removing the resist mask.   
     
     
         7 . The method for manufacturing a semiconductor device according to  claim 1  further comprising the step of:
 removing the region of the second conductive film after removing the resist mask. 
 
     
     
         8 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein a conductive film is provided under the first conductive film, and   wherein the conductive film comprises one of titanium, titanium nitride, tantalum, tantalum nitride, chromium, chromium nitride, niobium and niobium nitride.   
     
     
         9 . The method for manufacturing a semiconductor device according to  claim 4 ,
 wherein the oxide semiconductor comprises indium, zinc and oxide.