Semiconductor device, method for fabricating the same, and memory system including the semiconductor device
Semiconductor device, method for fabricating the same and electronic devices including the semiconductor device are provided. The semiconductor device comprises an interlayer insulating layer formed on a substrate and including a trench, a gate electrode formed in the trench, a first gate spacer formed on a side wall of the gate electrode to have an L shape, a second gate spacer formed on the first gate spacer to have an L shape and having a dielectric constant lower than that of silicon nitride, and a third spacer formed on the second gate spacer.
1. A semiconductor device comprising:
a gate electrode formed on a semiconductor substrate, the gate electrode having a first sidewall, a second sidewall, and a bottom surface extending between the first sidewall and second sidewall;
a gate dielectric film having a first portion, a second portion, and a third portion, the third portion formed between the bottom surface of the gate electrode and the semiconductor substrate, the first portion formed on the first sidewall of the gate electrode, the second portion formed on the second sidewall of the gate electrode;
a first gate spacer formed on the first portion of the gate dielectric film and a second gate spacer formed on the second portion of the gate dielectric film;
a third gate spacer formed on a sidewall of the first gate spacer and having a dielectric constant that is lower than a dielectric constant of the first gate spacer; and
an elevated source/drain formed at both sides of the gate electrode, a top surface of the elevated source/drain is higher than a top surface of the third portion of the gate dielectric film, and the elevated source/drain directly contacts at least the third gate spacer,
wherein, with respect to a vertical cross section, the maximum distance between outermost portions, with respect to the gate electrode, of an upper end of the first gate spacer and an upper end of the second gate spacer is less than the maximum distance between outermost portions, with respect to the gate electrode, of a lower end of the first gate spacer and a lower end of the second gate spacer.
2. The semiconductor device of claim 1 , further comprising a fourth gate spacer that is disposed on the third gate spacer and the fourth gate spacer is thicker than the third gate spacer.
3. The semiconductor device of claim 2 , wherein the elevated source/drain directly contacts the first and fourth gate spacers.
4. The semiconductor device of claim 1 , the third gate spacer has a dielectric constant that is lower than the dielectric constant of silicon nitride and higher than the dielectric constant of silicon oxide.
5. The semiconductor device of claim 1 , wherein the dielectric constant of the third gate spacer has a value between 4 and 6.
6. The semiconductor device of claim 1 , wherein the third gate spacer comprises SiOCN or SiOC.
7. The semiconductor device of claim 1 , wherein the first gate spacer and second gate spacer include silicon nitride.
8. The semiconductor device of claim 1 , wherein the gate electrode includes a first metal layer and a second metal layer.
9. The semiconductor device of claim 1 , further comprising an interlayer insulating layer disposed on the semiconductor substrate, and a top surface of the interlayer insulating layer and a top surface of the gate electrode are disposed on the same plane.