Semiconductor device and method of manufacturing the same

Abstract

According to one embodiment, a semiconductor device includes a switch element provided in a surface area of a semiconductor substrate, a contact plug with an upper surface and a lower surface, and a function element provided on the upper surface of the contact plug. The lower surface of the contact plug is connected to the switch element. The upper surface of the contact plug has a maximum roughness of 0.2 nm or less.

1 . A semiconductor device comprising:
 a switch in a surface area of a semiconductor substrate;   a contact plug with an upper surface and a lower surface, the lower surface connected to the switch, the upper surface having a roughness of 0.2 nm or less; and   a functional element on the upper surface of the contact plug.   
     
     
         2 . The device of  claim 1 ,
 wherein the functional element is a magnetoresistive element which comprises:
 a storage layer comprising a variable magnetization; 
 a reference layer comprising an invariable magnetization; and 
 a tunnel barrier layer between the storage layer and the reference layer, 
   wherein a roughness of a foundation of the tunnel barrier layer is 0.2 nm or less.   
     
     
         3 . The device of  claim 1 ,
 wherein the reference layer comprises first and second ferromagnetic layers and a nonmagnetic layer therebetween, and   wherein magnetization directions of the first and second ferromagnetic layers are opposite to each other.   
     
     
         4 . The device of  claim 1 ,
 wherein a foundation of the functional element comprises a material with a compressive stress.   
     
     
         5 . A method of manufacturing a semiconductor device, the method comprising:
 forming a contact plug by
 forming a first metal material; and 
 polishing the first metal material by a CMP-process until a roughness of an upper surface of the contact plug becomes 0.2 nm or less, and 
   wherein the CMP-process is executed by using an acid-slurry comprising a colloidal silica.   
     
     
         6 . The method of  claim 5 ,
 wherein the forming the contact plug is repeated twice or more.   
     
     
         7 . The method of  claim 5 , further comprising:
 forming the functional element on a lower electrode after forming the lower electrode on the contact plug,   wherein the forming the lower electrode comprises polishing a second metal material by the CMP-process after forming the second metal material on the contact plug.   
     
     
         8 . The method of  claim 5 , further comprising:
 forming the functional element on a lower electrode after forming the lower electrode on the contact plug,   wherein the forming the lower electrode comprises smoothing a second metal material by a gas cluster ion beam method after forming the second metal material on the contact plug.   
     
     
         9 . A method of manufacturing a semiconductor device, the method comprising:
 forming a contact plug by
 polishing a first metal material using a CMP-process after forming the first metal material, and 
 smoothing the first metal material using a gas cluster ion beam method after the forming the contact plug, 
   wherein the polishing and the smoothing are executed until a roughness of an upper surface of the contact plug becomes 0.2 nm or less.   
     
     
         10 . The method of  claim 9 ,
 wherein the polishing is repeated twice or more.   
     
     
         11 . The method of  claim 9 , further comprising:
 forming the functional element on a lower electrode after forming the lower electrode on the contact plug,   wherein the forming the lower electrode comprises smoothing a second metal material by a gas cluster ion beam method after forming the second metal material on the contact plug.