Method of fabricating a semiconductor device

Abstract

Provided is a semiconductor device having a backside illuminated image sensor and a method of forming same. The method includes providing a first substrate and a second substrate, forming metal interconnections on a first surface of the first substrate, forming a filling insulating layer filling spaces between sides of the metal interconnections and covering upper surfaces of the metal interconnections, forming a buffer insulating layer softer than the filling insulating layer on the filling insulating layer, forming a capping insulating layer denser than the buffer insulating layer on the buffer insulating layer, and bonding a surface of the capping insulating layer to a surface of the second substrate.

What is claimed is: 
     
         1 . A semiconductor device, comprising:
 a first substrate;   a set of metal interconnections formed on a first surface of the first substrate;   a filling insulating layer filling spaces between sides of the metal interconnections and covering upper surfaces of the metal interconnections;   a buffer insulating layer formed on the filling insulating layer;   a capping insulating layer formed on the buffer insulating layer; and   a second substrate bonded to a surface of the capping insulating layer.   
     
     
         2 . The device of  claim 1 , further comprising:
 field regions in the first substrate;   a photodiode between the field regions;   a recessed second surface of the first substrate;   a second surface insulating layer formed on the recessed second surface;   a plurality of color filters disposed on the second surface insulating layer; and   a plurality of microlenses formed on the color filters.   
     
     
         3 . The semiconductor device of  claim 1 , wherein the buffer insulating layer comprises a lower buffer insulating layer and an upper buffer insulating layer, and the lower and upper buffer insulating layers include the same material. 
     
     
         4 . The semiconductor device of  claim 1 , wherein the buffer insulating layer is softer than the filling insulating layer and the capping insulating layer is denser than the buffer insulating layer. 
     
     
         5 . The semiconductor device of  claim 1 , wherein the semiconductor device forms part of a mobile apparatus.