Semiconductor device with oxygen-containing metal gates

Abstract

A semiconductor device with oxygen-containing metal gates includes a substrate, a gate dielectric layer and a multi-layered stack structure. The multi-layered stack structure is disposed on the substrate. At least one layer of the multi-layered stack structure includes a work function metal layer. The concentration of oxygen in the side of one layer of the multi-layered stack structure closer to the gate dielectric layer is less than that in the side of one layer of the multi-layered stack structure opposite to the gate dielectric layer.

What is claimed is: 
     
         1 . A semiconductor device having a metal gate, comprising:
 a substrate;   a gate dielectric layer on the substrate; and   a multi-layered stack structure disposed on the gate dielectric layer, wherein at least one layer of the multi-layered stack structure comprises a work function metal layer, and a concentration of oxygen in the side of one layer of the multi-layered stack structure closer to the gate dielectric layer is less than a concentration of oxygen in the side of one layer of the multi-layered stack structure opposite to the gate dielectric layer.   
     
     
         2 . The semiconductor device having a metal gate according to  claim 1 , further comprising a metal layer disposed on the multi-layered stack structure, wherein the metal layer and the multi-layered stack structure together form a metal gate of the semiconductor device. 
     
     
         3 . The semiconductor device having a metal gate according to  claim 1 , wherein the multi-layered stack structure comprises two or more than two layers of metal/metal nitride. 
     
     
         4 . The semiconductor device having a metal gate according to  claim 1 , wherein the multi-layered stack structure comprises an etch stop layer, a barrier layer or a work function metal layer. 
     
     
         5 . The semiconductor device having a metal gate according to  claim 4 , wherein the etch stop layer comprises TiN, the barrier layer comprises TaN and the work function metal layer comprises TiN. 
     
     
         6 . The semiconductor device having a metal gate according to  claim 1 , wherein a dielectric constant of the gate dielectric layer is substantially greater than  4 , and the gate dielectric layer comprises hafnium oxide (HfO 2 ), hafnium silicon oxide (HfSiO 4 ), hafnium silicon oxynitride (HfSiON), aluminum oxide (Al 2 O 3 ), lanthanum oxide (La 2 O 3 ), lanthanum aluminum oxide (LaAlO), tantalum oxide (Ta 2 O 5 ), zirconium oxide (ZrO 2 ), zirconium silicon oxide (ZrSiO 4 ), hafnium zirconium oxide (HfZrO), yttrium oxide (Yb 2 O 3 ), yttrium silicon oxide (YbSiO), zirconium aluminate (ZrAlO), hafnium aluminate (HfAlO), aluminum nitride (AlN), titanium oxide (TiO 2 ), zirconium oxynitride (ZrON), hafnium oxynitride (HfON), zirconium silicon oxynitride (ZrSiON), hafnium silicon oxynitride (HfSiON), strontium bismuth tantalite (SrBi 2 Ta 2 O 9 , SBT), lead zirconate titanate (PbZr x Ti 1-x O 3 , PZT) or barium strontium titanate (Ba x Sr 1-x TiO 3 , BST).