Thin-film semiconductor device and method for manufacturing the same

1. A method of manufacturing a thin-film semiconductor device, which comprises:

forming an amorphous semiconductor layer on a transparent insulating substrate;

forming a crystallized region in the amorphous semiconductor layer;

forming a gate insulating film and a gate electrode on the crystallized region;

implanting an impurity at low concentration into an expected source region and an expected drain region of the crystallized region respectively neighboring to opposite sides of the gate electrode, the implanting being performed using the gate electrode as a mask;

forming an insulating film on a surface of the resultant structure;

etching back the insulating film until the crystallized region is exposed to thereby form a sidewall spacer on a sidewall of the gate electrode;

forming an amorphous semiconductor layer for forming a stacked source layer and a stacked drain layer on a surface of the resultant structure;

implanting an impurity at high concentration into the crystallized region and the amorphous semiconductor layer with the gate electrode and the sidewall spacer being used as a mask to thereby form a source diffusion region and a drain diffusion region in the crystallized region;

subjecting the amorphous semiconductor layer to heat treatment, thereby not only activating the impurity implanted in the crystallized region and the amorphous semiconductor layer but also restoring crystallinity of only a portion of the amorphous semiconductor layer which is formed on the crystallized region to thereby turn said portion into a polycrystalline semiconductor layer; and

subjecting the resultant surface to selective etching to thereby leave only the polycrystalline semiconductor layer which is deposited on the crystallized region and to remove the amorphous semiconductor layer formed on other regions, thereby forming, in a self-aligned manner, a stacked source diffusion layer consisting of polycrystalline semiconductor on the source diffusion layer and a stacked drain diffusion layer consisting of polycrystalline semiconductor on the drain diffusion layer.

2. The method according to claim 1 , which further comprises pre-amorphizing a surface layer of the crystallized region by implanting Si or Ge into the crystallized region prior to implanting an impurity at low concentration into an expected source region and an expected drain region, which are located in the crystallized regions respectively neighboring to the opposite sides of the gate electrode.

3. The method according to claim 1 , wherein the crystallized region is formed in the amorphous semiconductor layer by irradiation of laser beam to the amorphous semiconductor layer, thereby fusing and solidifying the amorphous semiconductor layer.

4. The method according to claim 1 , wherein the heat treatment is performed by a method selected from the group consisting of furnace annealing, rapid thermal annealing, flash lamp annealing and laser annealing.

5. The method according to claim 1 , wherein forming of a sidewall spacer on the sidewall of the gate electrode by subjecting the insulating film to an etch-back process until the crystallized region is exposed is performed by making use of a high-density plasma etching apparatus.

6. A method of manufacturing a thin-film semiconductor device, which comprises:

forming an amorphous semiconductor layer on a transparent insulating substrate; forming a crystallized region in the amorphous semiconductor layer;

forming a gate insulating film and a gate electrode on the crystallized region;

implanting an impurity at low concentration into an expected source region and an expected drain region of the crystallized region respectively neighboring to opposite sides of the gate electrode, the implanting being performed using the gate electrode as a mask;

forming an insulating film on a surface of the resultant structure;

etching back the insulating film until the crystallized region is exposed to thereby form a sidewall spacer on a sidewall of the gate electrode;

forming an amorphous semiconductor layer for forming a stacked source layer and a stacked drain layer on a surface of the resultant structure;

subjecting the amorphous semiconductor layer to a first heat treatment, thereby restoring crystallinity of only a portion of the amorphous semiconductor layer which is formed on the crystallized region to thereby turn said portion into a polycrystalline semiconductor layer;

subjecting the resultant surface to selective etching to thereby leave only the polycrystalline semiconductor layer which is formed on the crystallized region and to remove the amorphous semiconductor layer deposited on other regions;

implanting an impurity at high concentration into the crystallized region and the polycrystalline semiconductor layer with the gate electrode and the sidewall spacer being used as a mask to thereby form a source diffusion region and a drain diffusion region in the crystallized region and in the polycrystalline semiconductor layer; and

subjecting the crystallized region and the polycrystalline semiconductor layer to a second heat treatment to thereby activate impurity implanted into the crystallized region and the polycrystalline semiconductor layer.

7. The method according to claim 6 , which further comprises a first pre-amorphizing for pre-amorphizing a surface layer of the crystallized region by implanting Si or Ge into the polycrystalline semiconductor layer prior to implanting an impurity at high concentration into the crystallized regions and the polycrystalline semiconductor layer; and a second pre-amorphizing for amorphizing a surface layer of the polycrystalline semiconductor layer by the implantation of Si or Ge into the polycrystalline semiconductor layer which is left in the crystallized region due to the selective etching prior to implanting an impurity at high concentration into the crystallized regions and the polycrystalline semiconductor layer.

8. The method according to claim 6 , wherein the crystallized region is formed in the amorphous semiconductor layer by irradiation of laser beam to the amorphous semiconductor layer, thereby fusing and solidifying the amorphous semiconductor layer.

9. The method according to claim 6 , wherein the first and second heat treatments is performed by a method selected from the group consisting of furnace annealing, rapid thermal annealing, flash lamp annealing and laser annealing.

10. The method according to claim 6 , wherein forming of a sidewall spacer on the sidewall of the gate electrode by etching back the insulating film until the crystallized region is exposed is performed by making use of a high-density plasma etching apparatus.

11. A method of manufacturing a thin-film semiconductor device, which comprises:

forming an amorphous semiconductor layer on a transparent insulating substrate;

forming a crystallized region in the amorphous semiconductor layer;

forming a gate insulating film and a gate electrode on the crystallized region;

implanting an impurity at low concentration into an expected source region and an expected drain region of the crystallized regions respectively neighboring to opposite sides of the gate electrode, the implanting being performed using the gate electrode as a mask;

forming an insulating film on a surface of the resultant structure;

etching back the insulating film until the crystallized region is exposed to thereby form a sidewall spacer on a sidewall of the gate electrode;

forming an amorphous semiconductor layer for forming a stacked source layer and a stacked drain layer on a surface of the resultant structure;

implanting an impurity at high concentration into the crystallized region and the amorphous semiconductor layer with the gate electrode and the sidewall spacer being used as a mask to thereby form a source diffusion region and a drain diffusion region in the crystallized region;

subjecting the amorphous semiconductor layer to a first heat treatment, thereby not only activating impurity implanted in the crystallized region and the amorphous semiconductor layer but also restoring the crystallinity of only a portion of the amorphous semiconductor layer which is formed on the crystallized region to thereby turn said portion into a polycrystalline semiconductor layer;

subjecting the resultant surface to selective etching to thereby leave only the polycrystalline semiconductor layer which is formed on the crystallized region and to remove the amorphous semiconductor layer formed on other regions, thereby forming, in a self-aligned manner, a stacked source diffusion layer formed of polycrystalline semiconductor on the source diffusion layer and a stacked drain diffusion layer formed of polycrystalline semiconductor on the drain diffusion layer;

forming a high-melting point metal layer on a surface of resultant structure;

subjecting a resultant surface to a second heat treatment to thereby form a silicide film at an interface between the stacked source diffusion layer and the high-melting point metal layer and at an interface between the stacked drain diffusion layer and the high-melting point metal layer;

removing unreacted high-melting point metal layer, leaving the silicide film on the stacked drain diffusion layer and on the stacked drain diffusion layer; and

subjecting a resultant surface to a third heat treatment to thereby accomplish the silicidation and form a source diffusion region including the source diffusion region, the stacked source diffusion layer and the silicide film, and a drain diffusion region including the drain diffusion region, the stacked source diffusion layer and the silicide film on opposite sides of the gate electrode.

12. The method according to claim 11 , wherein the crystallized region is formed in the amorphous semiconductor layer by the irradiation of laser beam to the amorphous semiconductor layer, thereby fusing and solidifying the amorphous semiconductor layer.

13. The method according to claim 11 , wherein the first, second and third heat treatments is performed by a method selected from the group consisting of furnace annealing, rapid thermal annealing, flash lamp annealing and laser annealing.

14. The method according to claim 11 , wherein forming of the sidewall spacer on the sidewall of the gate electrode by etching back the insulating film until the crystallized region is exposed is performed by making use of a high-density plasma etching apparatus.

15. The method according to claim 11 , which further comprises a first pre-amorphizing for amorphizing a surface layer of the crystallized region by implanting Si or Ge into the crystallized region prior to implanting an impurity at low concentration into an expected source region and an expected drain region of the crystallized regions respectively neighboring to the opposite sides of the gate electrode.

16. The method according to claim 15 , wherein implanting an impurity at high concentration is performed subsequent to the first heat treatment.

17. The method according to claim 15 , wherein implanting an impurity at high concentration is performed subsequent to the second heat treatment.

18. The method according to claim 16 , which further comprises a second pre-amorphizing for amorphizing a surface layer of the polycrystalline semiconductor layer by the implantation of Si or Ge into the polycrystalline semiconductor layer which is left in the crystallized region due to the selective etching.

19. The method according to claim 15 , wherein the high-melting point metal is one metal selected from the group consisting of Ni, Ti, Co, Mo and W.