Semiconductor device having vertical channel transistor and method for fabricating the same
A semiconductor device having a substrate; a plurality of pillar structures, wherein each pillar structure includes an active pillar disposed over the substrate; a gate electrode surrounding an outer wall of the active pillar; an interlayer dielectric (ILD) layer insulating adjacent pillar structures; a gate contact penetrating the ILD layer and configured to connect to a sidewall of the gate electrode; and a word line connected to the gate contact.
1. A method for fabricating a semiconductor device, the method comprising:
forming a plurality of pillar structures disposed over a substrate, each of the pillar structures including an active pillar and a hard mask layer;
forming a gate electrode surrounding an outer wall of the active pillar;
forming an interlayer dielectric (ILD) layer insulating adjacent pillar structures;
forming a gate contact penetrating the ILD layer, the gate contact configured to connect to a sidewall of the gate electrode; and
forming a word line connected to the gate contact, the word line being formed to have a continuous line shape over the pillar structures,
wherein the word line is formed directly on the gate contact and the hard mask layer.
2. The method of claim 1 , wherein the forming of the gate contact comprises:
forming a contact hole by etching the ILD layer to a depth that partially exposes a surface of the gate electrode; and
filling the contact hole with a conductive layer to form the gate contact.
3. The method of claim 1 , wherein the forming of the word line includes forming the word line with a material having a lower sheet resistance than the gate electrode and the gate contact.
4. The method of claim 3 , wherein the gate electrode and the gate contact include a polysilicon layer.
5. The method of claim 3 , wherein the word line includes a metal-containing layer.
6. The method of claim 5 , wherein the metal-containing layer includes at least one of tungsten nitride (WN), titanium nitride (TiN), tantalum nitride (TaN), tungsten (W), ruthenium (Ru), cobalt (Co), molybdenum (Mo), titanium (Ti), tantalum (Ta) and a metal silicide.
7. The method of claim 1 , wherein the word line and the gate contact include a material having a lower sheet resistance than the gate electrode.
8. The method of claim 7 , wherein the gate electrode includes a polysilicon layer.
9. The method of claim 7 , wherein the word line and the gate contact includes a metal-containing layer.
10. The method of claim 1 , wherein the word line and the pillar structure partially overlap each other.
11. The method of claim 10 , wherein the word line is formed in a zigzag shaped wave pattern.
12. The method of claim 1 , further comprising:
forming a storage node contact facing the gate contact, the storage node contact being configured to connect to the active pillar after forming the word line, the pillar structure being interposed between the storage node contact and the gate contact.
13. The method of claim 12 , wherein the forming of the storage node contact comprises:
forming an ILD layer insulating the word lines from each other;
etching portions of the ILD layer and the hard mask layer to form a primary contact hole;
forming a spacer on a sidewall of the primary contact hole;
forming a secondary contact hole aligned with the spacer by performing an etching process until an upper region of the active pillar is exposed; and
forming a conductive layer to fill the secondary contact hole, and planarizing the conductive layer.
14. The method of claim 13 , wherein the spacer includes a nitride layer.