Semiconductor device and its manufacturing method
View Patent ↗A semiconductor device including memory cells isolated by a trench that may be self aligned with a stacked film pattern ( 7 ) has been disclosed. The memory cells may be flash memory cells having an active gate film ( 2 ) that may be thinner than a gate oxide film ( 30 ). The active gate film ( 2 ) may be located in a central portion under of a gate electrode ( 3 ). The gate oxide film ( 30 ) may be located under end portions of the gate electrode ( 3 ). In this way, a distance between a shoulder portion of a trench ( 11 ) and a gate electrode ( 3 ) may be increased. Thus, an electric field concentration in the shoulder portion of the trench ( 11 ) may be decreased and memory cell characteristics may be improved.
1. A semiconductor device, comprising:
a semiconductor substrate;
an isolation film buried in trenches in the semiconductor substrate;
a gate insulating film of a transistor formed between the isolation film and having end portions adjacent to the isolation film that are thicker than a central portion in a first direction that does not intersect a source/drain region of the transistor;
a first electrode formed on the gate insulating film;
a capacitance insulating film formed on the first electrode;
a second electrode formed on the capacitance insulating film; and
one of the trenches in the semiconductor substrate between adjacent gate insulating films has a width essentially the same as the distance between the adjacent insulating films
wherein the first electrode has end portions extending over a portion of the isolation film.
2. The semiconductor device according to claim 1 , wherein:
the central portion of the gate insulating film has a thickness of approximately 7 to 11 nm.
3. The semiconductor device according to claim 1 , wherein:
the capacitance insulating film includes nitride.
4. The semiconductor device according to claim 1 , wherein:
the capacitance insulating film includes an ONO film.
5. The semiconductor device according to claim 1 , wherein:
an upper surface of the isolation film extending above the one of the trenches is higher than an upper surface of the end portion of the gate insulating film under the first electrode.
6. The semiconductor device according to claim 1 , wherein:
the trench has a depth in the semiconductor substrate of approximately 0.2 to 0.3 μm.
7. A semiconductor device, comprising:
a semiconductor substrate;
an isolation film buried in trenches in the semiconductor substrate;
a gate insulating film of a transistor formed between the isolation film and having end portions adjacent to the isolation film that are thicker than a central portion in a first direction that does not intersect a source/drain region of the transistor;
a first electrode formed on the gate insulating film;
a capacitance insulating film formed on the first electrode; and
a second electrode formed on the capacitance insulating film
wherein the first electrode formed on the gate insulating film and having a recessed portion at a central first electrode portion between adjacent isolation films.
8. The semiconductor device according to claim 7 , wherein:
an upper surface of the isolation film extending above one of the trenches is at substantially the same height as an upper surface of the end portion of the gate insulating film under the first electrode.
9. The semiconductor device according to claim 7 , wherein:
an upper surface of the isolation film extending above one of the trenches is at substantially the same height as an upper surface of an end first electrode portion of the first electrode.
10. The semiconductor device according to claim 1 , wherein:
the semiconductor device is a flash memory.
11. The semiconductor device of claim 1 , wherein:
the end portions of the gate insulating film have a thickness of approximately 20 to 50 nm.
12. A semiconductor device, comprising:
a semiconductor substrate;
an isolation film buried in trenches in the semiconductor substrate; and
a gate insulating film of a transistor formed between the isolation film and having end portions adjacent to the isolation film that are thicker than a central portion in a first direction that does not intersect a source/drain region of the transistor, wherein
an upper surface of the end portion and an upper surface of the isolation film are in an essentially same position.
13. The semiconductor device according to claim 12 , further comprising:
a first electrode formed on the gate insulating film.
14. The semiconductor device according to claim 13 , wherein:
one of the trenches in the semiconductor substrate between adjacent gate insulating films has a width essentially the same as the distance between the adjacent insulating films.
15. The semiconductor device according to claim 14 , wherein:
the first electrode has end portions extending over a portion of the isolation film.
16. The semiconductor device according to claim 14 , wherein:
an upper surface of the isolation film extending above the one of the trenches is higher than an upper surface of the end portion of the gate insulating film under the first electrode.
17. A semiconductor device, comprising:
a semiconductor substrate;
an isolation film buried in trenches in the semiconductor substrate;
a gate insulating film of a transistor formed between the isolation film and having end portions adjacent to the isolation film that are thicker than a central portion in a first direction that does not intersect a source/drain region of the transistor; and
a first electrode formed on the gate insulating film
wherein the first electrode formed on the gate insulating film and having a recessed portion at a central first electrode portion between adjacent isolation films.
18. The semiconductor device according to claim 17 , wherein:
an upper surface of the isolation film extending above one of the trenches is at substantially the same height as an upper surface of the end portion of the gate insulating film under the first electrode.
19. The semiconductor device according to claim 17 , wherein:
an upper surface of the isolation film extending above one of the trenches is at substantially the same height as an upper surface of an end first electrode portion of the first electrode.
20. A semiconductor device, comprising:
a semiconductor substrate;
an isolation film buried in trenches in the semiconductor substrate; and
a gate insulating film of a transistor formed between the isolation film and having end portions adjacent to the isolation film that are thicker than a central portion in a first direction that does not intersect a source/drain region of the transistor, wherein
a width of at least one of the trenches decreases monotonically toward a bottom of the at least one of the trenches.