Semiconductor device and fabricating method thereof
The semiconductor device includes a substrate, a trench formed in the substrate, a gate insulation layer conformally formed on the inner surface of the trench, buried gate electrodes formed on the gate insulation layer and filling a portion of the trench, and a capping layer formed on the buried gate electrodes and filling the trench. The buried gate electrode include a first gate electrode and a second gate electrode surrounding a bottom portion of the first gate electrode, and an air gap is provided between a top portion of the first gate electrode and the gate insulation layer.
1. A semiconductor device comprising:
a substrate;
a trench formed in the substrate;
a gate insulation layer conformally formed on the inner surface of the trench;
a buried gate electrode formed on the gate insulation layer and filling a portion of the trench; and
a capping layer formed on the buried gate electrodes and filling the trench,
wherein the buried gate electrode includes a first gate electrode and a second gate electrode surrounding a bottom portion of the first gate electrode, and an air gap is provided between a top portion of the first gate electrode and the gate insulation layer.
2. The semiconductor device of claim 1 , wherein the capping layer is formed on the first gate electrode and the air gap.
3. The semiconductor device of claim 1 , wherein the air gap is surrounded by the first gate electrode, the second gate electrode, the gate insulation layer and the capping layer.
4. The semiconductor device of claim 1 , wherein the second gate electrode surrounds sidewalls of the bottom portion of the first gate electrode and a bottom surface of the first gate electrode.
5. The semiconductor device of claim 1 , wherein the air gap is formed at opposite sides of the first gate electrode.
6. The semiconductor device of claim 1 , wherein the first gate electrode includes tungsten (W).
7. The semiconductor device of claim 1 , wherein the second gate electrode includes titanium nitride (TiN) or tungsten nitride (WN).
8. The semiconductor device of claim 1 , wherein the capping layer includes silicon nitride (SiN).
9. The semiconductor device of claim 1 , wherein the air gap is surrounded by the first gate electrode, the second gate electrode, the gate insulation layer and the capping layer.
10. The semiconductor device of claim 1 , wherein the second gate electrode surrounds sidewalls of the bottom portion of the first gate electrode and a bottom surface of the first gate electrode.
11. A semiconductor device including a switch transistor comprising;
a substrate;
a trench formed in the substrate;
a gate insulation layer conformally formed on the inner surface of the trench;
a buried gate electrode formed on the gate insulation layer and filling a portion of the trench;
a capping layer formed on the buried gate electrodes and filling the trench; and
a source/drain formed in the substrate adjacent to the buried gate electrode;
wherein the buried gate electrode includes a first gate electrode and a second gate electrode surrounding a bottom portion of the first gate electrode, and an air gap is provided between a top portion of the first gate electrode and the gate insulation layer.
12. The semiconductor device of claim 11 , further comprising a capacitor or a magnetic tunnel junction connected to the switch transistor.
13. The semiconductor device of claim 11 , wherein the capping layer is formed on the first gate electrode and the air gap.