Semiconductor device and method for fabricating the same
A semiconductor device includes a step-type recess pattern formed in a substrate, a gate electrode buried in the recess pattern and having a gap disposed between the gate electrode and upper sidewalls of the recess pattern, an insulation layer filling the gap, and a source and drain region formed in a portion of the substrate at two sides of the recess pattern. The semiconductor device is able to secure a required data retention time by suppressing the increase of leakage current caused by the reduction of a design rule.
1. A semiconductor device, comprising:
a step-type saddle fin recess pattern formed in a substrate including an active region and an isolation region;
a gate electrode buried in the recess pattern and having a gap disposed between the gate electrode and upper sidewalls of the recess pattern;
an insulation layer filling the gap; and
a source region and a drain region formed in portions of the substrate at opposite sides of the recess pattern by doping impurities into the substrate,
wherein the recess pattern comprises:
a first pattern crossing the isolation region and the active region at the same time;
a second pattern connected to a bottom of the first pattern in the active region and having the width smaller than the width of the first pattern: and
a third pattern connected to the bottom of the first pattern in the isolation region, having the width smaller than the width of the first pattern, and exposing a lower surface and lower sidewalls of the second pattern with a saddle fin structure.
2. The semiconductor device of claim 1 , wherein the recess pattern comprises a line shape crossing both of the isolation region and the active region.
3. The semiconductor device of claim 1 , wherein the width of the second pattern is substantially the same as the width of the third pattern.
4. The semiconductor device of claim 1 , wherein, among the first to third patterns, the third pattern has the greatest depth and the first pattern has the smallest depth.
5. The semiconductor device of claim 1 , wherein the width of the gate electrode is equal to or greater than the width of the second pattern.
6. The semiconductor device of claim 1 , further comprising a gate insulation layer formed between the recess pattern and the gate electrode, wherein the width of the gap is greater than the thickness of the gate insulation layer.
7. The semiconductor device of claim 1 , wherein the insulation layer fills the gap and covers sidewalls of the gate electrode.
8. The semiconductor device of claim 1 , wherein the insulation layer comprises a single layer or a stacked layer selected from a group consisting of an oxide layer, a nitride layer and an oxynitride layer.
9. The semiconductor device of claim 1 , wherein a work function of the source and drain region is equal to a work function of the gate electrode, or an absolute value of the work function difference of the source and drain region and the gate electrode is smaller than 0.5 eV.
10. The semiconductor device of claim 1 , wherein the gate electrode comprises a single layer formed of a semiconductor layer or a metallic layer, or a stacked layer of the semiconductor layer and the metallic layer.
11. The semiconductor device of claim 10 , wherein the semiconductor layer comprises a polysilicon layer and the metallic layer comprises a tungsten layer.