Semiconductor device and manufacturing method thereof
View Patent ↗A semiconductor device includes a substrate including a semiconductor layer at a surface, a gate insulating film disposed on the semiconductor layer, and a gate electrode disposed on the gate insulating film. The gate electrode includes a conductive layer consisting of a nitride of a predetermined metal in contact with the gate insulating film. The conductive layer is formed by stacking a first film consisting of a nitride of the predetermined metal and a second film consisting of the predetermined metal, and diffusing nitrogen from the first film to the second film by solid-phase diffusion.
1. A semiconductor device, comprising:
a substrate including a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type at a surface;
first and second gate insulating films disposed on the first and second semiconductor layers, respectively;
a first gate electrode disposed on the first gate insulating film, and including a first conductive layer consisting of a nitride of a predetermined metal in contact with the first gate insulating film, the first conductive layer having a first nitrogen concentration; and
a second gate electrode disposed on the second gate insulating film, and including a second conductive layer consisting of a nitride of the predetermined metal in contact with the second gate insulating film, the second conductive layer having a second nitrogen concentration lower than the first nitrogen concentration,
wherein the first conductive layer is formed from a first film consisting of a nitride of the predetermined metal, and the second conductive layer is formed by stacking the first film and a second film consisting of the predetermined metal, and diffusing nitrogen from the first film to the second film by diffusion, and
wherein the first gate electrode further comprises a portion derived from the second film and stacked on the first conductive layer through an electrically-conductive barrier layer for preventing nitrogen diffusion.
2. The device according to claim 1 , further comprising a first pair of source/drain layers formed in the first semiconductor layer one on either side of the first gate electrode, and a second pair of source/drain layers formed in the second semiconductor layer one on either side of the second gate electrode.
3. The device according to claim 1 , wherein the predetermined metal is selected from a group consisting of Ta and W.
4. The device according to claim 1 , wherein the first semiconductor layer is a p-type silicon layer and the second semiconductor layer is an n-type silicon layer, and wherein the first conductive layer has a work function of 3.9 to 4.2 eV and the second conductive layer has a work function of 4.8 to 5.3 eV.
5. The device according to claim 1 , wherein the first conductive layer has a first thickness T 1 and a first nitrogen concentration C 1 , and the second conductive layer has a second thickness T 2 and a second nitrogen concentration C 2 , to satisfy C 1 >C 2 , T 1 <T 2 , and C 1 ×T 1 ≅C 2 ×T 2 .
6. The device according to claim 1 , wherein the barrier layer is a TiN layer.
7. The device according to claim 6 , wherein the TiN layer has a thickness of 10 to 20 nm.
8. A semiconductor device, comprising:
a substrate including a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type at a surface;
first and second gate insulating films disposed on the first and second semiconductor layers, respectively;
a first gate electrode disposed on the first gate insulating film, and including a first conductive layer consisting of a nitride of a predetermined metal in contact with the first gate insulating film, the first conductive layer having a first thickness T 1 and a first nitrogen concentration C 1 ; and
a second gate electrode disposed on the second gate insulating film, and including a second conductive layer consisting of a nitride of the predetermined metal in contact with the second gate insulating film, the second conductive layer having a second thickness T 2 and a second nitrogen concentration C 2 ,
wherein the device is arranged to satisfy C 1 >C 2 , T 1 <T 2 , and C 1 ×T 1 ≅C 2 ×T 2 , and
wherein the first gate electrode further comprises an upper layer consisting of the predetermined metal and stacked on the first conductive layer through an electrically-conductive barrier layer for preventing nitrogen diffusion.
9. The device according to claim 8 , wherein the first semiconductor layer is a p-type silicon layer and the second semiconductor layer is an n-type silicon layer, and wherein the first conductive layer has a work function of 3.9 to 4.2 eV and the second conductive layer has a work function of 4.8 to 5.3 eV.
10. The device according to claim 8 , wherein the predetermined metal is selected from a group consisting of Ta and W, and the barrier layer is a TiN layer.
11. A semiconductor device, comprising:
a substrate including a first semiconductor layer of a p-type and a second semiconductor layer of an n-type at a surface;
first and second gate insulating films disposed on the first and second semiconductor layers, respectively;
a first gate electrode disposed on the first gate insulating film, and including a first conductive layer consisting of TaN in contact with the first gate insulating film, the first conductive layer having a first thickness T 1 and a first nitrogen concentration C 1 ;
a second gate electrode disposed on the second gate insulating film, and including a second conductive layer consisting of TaN in contact with the second gate insulating film, the second conductive layer having a second thickness T 2 and a second nitrogen concentration C 2 ;
a first pair of source/drain layers formed in the first semiconductor layer, one of the first pair of source/drain layers positioned on either side of the first gate electrode; and
a second pair of source/drain layers formed in the second semiconductor layer, one of the second pair of source/drain layers positioned on either side of the second gate electrode,
wherein the device is arranged to satisfy C 1 >C 2 , T 1 <T 2 , and C 1 ×T 1 ≅C 2 ×T 2 , and
wherein the first gate electrode further comprises an upper layer consisting of Ta and stacked on the first conductive layer through a barrier layer formed of a TiN layer for preventing nitrogen diffusion.
12. The device according to claim 11 , wherein the first semiconductor layer is a p-type silicon layer and the second semiconductor layer is an n-type silicon layer, and wherein the first conductive layer has a work function of 3.9 to 4.2 eV and the second conductive layer has a work function of 4.8 to 5.3 eV.
13. The device according to claim 11 , wherein the TiN layer has a thickness of 10 to 20 nm.