Nonvolatile semiconductor memory device and method of manufacturing the same

Abstract

According to one embodiment, a nonvolatile semiconductor memory device includes a magnetoresistive element formed on a semiconductor substrate, a first contact plug which extends through an interlayer dielectric film formed on the semiconductor substrate and immediately below the magnetoresistive element, has a bottom surface in contact with an upper surface of the semiconductor substrate, and is adjacent to the magnetoresistive element, and an insulating film formed between the magnetoresistive element and the first contact plug and on the interlayer dielectric film, wherein the insulating film includes a first region positioned on a side of the interlayer dielectric film, and a second region positioned in the insulating film and on an upper surface of the first region, the insulating film is made of SiN, and the first region is a nitrogen rich film compared to the second region.

What is claimed is: 
     
         1 . A nonvolatile semiconductor memory device manufacturing method comprising:
 forming a magnetoresistive element on a semiconductor substrate;   forming a first insulating film along an upper surface and sidewall of the magnetoresistive element and along an interlayer dielectric layer formed immediately below the magnetoresistive element;   forming a second insulating film which is nitrogen-rich compared to the first insulating film by plasma nitridation to the first insulating film;   depositing a third insulating film on the second insulating film; and   forming a contact plug which extends through the third insulating film, the second insulating film, and the interlayer dielectric layer, and has a bottom surface in contact with an upper surface of the semiconductor substrate.   
     
     
         2 . The method according to  claim 1 , wherein each of the second insulating film and the third insulating film is made of SiN. 
     
     
         3 . The method according to  claim 2 , wherein a thickness of the insulating film formed on the upper surface and the interlayer dielectric layer is larger than that of the insulating film formed on the sidewall. 
     
     
         4 . The method according to  claim 3 , wherein
 the thickness of the insulating film formed on the upper surface and the interlayer dielectric layer is 3 to 4 nm, and   the thickness of the insulating film formed on the sidewall is 1 to 2 nm.   
     
     
         5 . The method according to  claim 1 , wherein the second insulating film formed on the sidewall has a dielectric constant higher than that of the third insulating film.