Semiconductor memory

• US 4,901,128 A
• Filed: 11/24/1986
• Issued: 02/13/1990
• Est. Priority Date: 11/04/1982
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sakai, Yoshio, Koyanagi, Mitsumasa, Shimizu, Shinji, Miyao, Masanobu, Kure, Tokuo, Kawamoto, Yoshifumi, Sunami, Hideo, Shimohigashi, Katsuhiro, Masuhara, Toshiaki, Minato, Osamu
• Primary Examiner(s): Hille, Rolf
• Assistant Examiner(s): Limanek, Robert P.
• Application Number:
  US06/934,556
• Time in Patent Office: 1,177 Days
• Field of Search: 357/23.6, 357/41, 357/55
• US Class Current: 257/301
• CPC Class Codes: G11C 11/404 with one charge-transfer gate, e.g. MOS transistor, per cell
• CPC Class Codes: H01L 29/945 Trench capacitors
• CPC Class Codes: H10B 12/37 the capacitor being at least partially in a trench in the substrate
• CPC Class Codes: H10B 12/395 the transistor being vertical

Abstract

A semiconductor memory comprises a capacitor with a data storage portion, and an insulated-gate field-effect transistor. The capacitor is formed by a plate which is made up of the side walls and base of a groove formed in a semiconductor substrate, and by a capacitor electrode formed on the side walls and the base, over an insulation film, and which is connected electrically to the source or drain of the insulated-gate field-effect transistor. Various embodiments are provided for reducing size and preventing leakage between other memory cells, including forming stacked capacitors, forming the transistor over the capacitor, using a silicon-over-insulator arrangement for the transistor, forming a common capacitor plate and providing high impurity layers within the substrate.

Claims

1. A semiconductor memory which includes a plurality of word lines, a plurality of bit lines, and a plurality of memory cells, each memory cell including an insulated-gate field-effect transistor and a capacitor with a data storage portion formed on a semiconductor surface region having a first conductivity type, wherein said insulated-gate field-effect transistor comprises:

a gate electrode electrically connected to one of the plurality of word lines,

a source and drain provided in the semiconductor surface region, one of the plurality of bit lines being connected to the drain or source of the insulated-gate field-effect transistor, and

a gate insulation film provided between the semiconductor surface region and the gate electrode, the gate insulation film being formed less than 50 nm; and

wherein said capacitor comprises;

a groove formed into the semiconductor surface region, wherein a depth of the groove is more than 1 μ

m, wherein the depth of the groove is greater than a distance between inner walls of the grooves, and wherein the semiconductor surface region surrounding the groove acts as a first electrode,

a capacitor insulation film formed on a surface of the groove, wherein the capacitor insulation film comprises a composite film of SiO₂ and Si₃ N₄, and

a second electrode formed in the groove over the capacitor insulation film, the second electrode being connected to the source or drain of the insulated-gate field-effect transistor, wherein the second electrode comprises a polycrystalline silicon, and wherein the groove is filled with the second electrode,

wherein an individual groove is provided for forming the capacitor for each memory cell.

2. A semiconductor memory according to claim 1, wherein the first electrode comprises an impurity region formed into the semiconductor surface region, and wherein an impurity concentration of the region is higher than an impurity concentration of the semiconductor surface region.

3. A semiconductor memory according to claim 1, wherein said first conductivity is n-type, and wherein the first electrode is set at ground potential.

4. A semiconductor memory according to claim 2, wherein the impurity region is commonly formed between predetermined pairs of adjacent ones of said plurality of memory cells, and wherein the depth of the groove is more than 2 μ

m.

5. A semiconductor memory according to claim 1, wherein the gate electrode comprises at least one material selected from polycrystalline silicon, molybdenum silicide, molybdenum, and tungsten.

6. A semiconductor memory according to claim 1, wherein the plurality of word lines comprises at least one material elected from polycrystalline silicon, molybdenum silicide, molybdenum, and tungsten, and the plurality of bit lines comprises Al.

7. A semiconductor memory according to claim 1, wherein the plurality of memory cells is arranged as a folded-bit line construction.

8. A semiconductor memory according to claim 1, wherein the plurality of memory cells is arranged as an open-bit line construction.

9. A semiconductor memory according to claim 1, wherein the drain or source of the insulated-gate field-effect transistor is commonly formed between predetermined pairs of adjacent ones of said plurality of memory cells.

10. A semiconductor memory which includes a plurality of word lines, a plurality of bit lines, and a plurality of memory cells, each memory cell including an insulated-gate field-effect transistor and a capacitor, wherein said insulated-gate field-effect transistor comprises:

a gate electrode electrically connected to one of the plurality of word lines, wherein the gate electrode comprises at least one material selected from polycrystalline silicon, molybdenum silicide, molybdenum, and tungsten,

a source and drain provided in a semiconductor surface region having first conductivity type, one of the plurality of bit lines being connected to the drain or source of the insulated-gate field-effect transistor, wherein the drain or source of the insulated-gate field-effect transistor is commonly formed between predetermined pairs of adjacent ones of said plurality of memory cells, and

a gate insulation film provided between the semiconductor surface region and the gate electrode, the gate insulation film being formed less than 50 nm; and

wherein said capacitor comprises;

a groove formed into the semiconductor surface region, wherein a depth of the groove is more than 1 μ

m, wherein the depth of the groove is greater than a distance between inner walls of the groove, and wherein the semiconductor surface region surrounding the groove acts as a first electrode,

a capacitor insulation film formed on a surface of the groove, wherein the capacitor insulation film comprises a composite film of SiO₂ and Si₃ N₄, and

a second electrode formed in the groove over the capacitor insulation film, the second electrode being connected to the source or drain of the insulated-gate field-effect transistor, wherein the second electrode comprises a polycrystalline silicon, and wherein the groove is filled with the second electrode,

wherein an individual groove is provided for forming the capacitor for each memory cell.

11. A semiconductor memory according to claim 10, wherein the first electrode comprises an impurity region formed into the semiconductor surface region, and wherein an impurity concentration of the region is higher than an impurity concentration of the semiconductor surface region.

12. A semiconductor memory according to claim 10, wherein the plurality of word lines comprises at least one material selected from polycrystalline silicon, molybdenum silicide, molybdenum, and tungsten, and the plurality of bit lines comprises Al.

13. A semiconductor memory according to claim 10, wherein said first conductivity is n-type, and wherein the first electrode is set at ground potential.

14. A semiconductor memory according to claim 11, wherein the impurity region is commonly formed between predetermined pairs of adjacent ones of said plurality of memory cells, and wherein the depth of the groove is more than 2 μ

m.

15. A semiconductor memory according to claim 10, wherein the plurality of memory cells is arranged as a folded-bit line construction.

16. A semiconductor memory according to claim 10, wherein the plurality of memory cells is arranged as an open-bit line construction.

17. A semiconductor memory which includes a plurality of word lines, a plurality of bit lines, and a plurality of memory cells, each memory cell including an insulated-gate field-effect transistor and a capacitor, wherein said insulated-gate field-effect transistor comprises:

a gate electrode electrically connected to one of the plurality of word lines, wherein the gate electrode comprises at least one material selected from polycrystalline silicon, molybdenum silicide, molybdenum, and tungsten,

a source and drain provided in a semiconductor surface region having a first conductivity type, one of the plurality of bit lines being connected to the drain or source of the insulated-gate field-effect transistor, wherein the drain or source of the insulated-gate and field-effect transistor is commonly formed between predetermined pairs of adjacent ones of said plurality of memory cells, and

a gate insulation film provided between the semiconductor surface region and the gate electrode; and

wherein said capacitor comprises;

a groove formed into the semiconductor surface region, wherein a depth of the groove is more than 2 μ

m, the depth of the groove is greater than a distance between inner walls of the groove, and the semiconductor surface region surrounding the groove acts as a first electrode, wherein the first electrode comprises an impurity region formed into the semiconductor surface region, wherein the region is commonly formed between predetermined pairs of adjacent ones of said plurality of memory cells,

a capacitor insulation film formed on a surface of the groove, wherein the capacitor insulation film comprises a three-layer composite film of SiO₂, Si₃ N₄, SiO₂, and

a second electrode formed in the groove over the capacitor inulation film, the second electrode being connected to the source or drain of the insulated-gate field-effect transistor,

wherein an individual groove is provided for forming the capacitor for each memory cell.

18. A semiconductor memory according to claim 17, wherein the plurality of word lines comprises at least one material selected from polycrystalline silicon, molybdenum silicide, molybdenum, and tungsten, and the plurality of bit lines comprises Al.

19. A semiconductor memory according to claim 17, wherein said first conductivity is n-type, and wherein the first electrode is set at ground potential.

20. A semiconductor memory according to claim 17, wherein the plurality of memory cells is arranged as a folded-bit line construction.

21. A semiconductor memory according to claim 17, wherein the plurality of memory cells is arranged as an open-bit line construction.