Semiconductor device incorporating thyristor-based memory and strained silicon
View Patent ↗A semiconductor memory device may comprise a thyristor-based memory having some portions formed in strained silicon, and other portions formed in relaxed silicon. In a further embodiment, a thyristor in the thyristor-based memory may be formed in a region of relaxed silicon germanium, while an access device to the thyristor-based memory may have a body region incorporating a portion of a layer of strained silicon. In yet a further embodiment, different regions of the thyristor may be formed in vertical aligned relationship relative to an upper surface of the relaxed silicon germanium. For this embodiment, the thyristor may be formed substantially within the depth of the relaxed silicon germanium layer. In a method of forming the semiconductor device, relaxed silicon may be deposited over exposed regions of a silicon substrate, and a thin layer of strained silicon formed over a portion of the substrate having silicon germanium.
1. A semiconductor device comprising:
a first region comprising relaxed silicon;
a second region comprising strained silicon on silicon germanium;
a thyristor-based memory array comprising thyristor-based memory elements formed at least in part within the first regions, and read/write interface circuits formed at least in part in the second regions; and
insulating material of a supporting substrate;
wherein the relaxed silicon of the first region and the silicon germanium of the second region are each over different portions of the insulating material.
2. The device of claim 1 , the supporting substrate supporting the insulating material on a side thereof opposite the relaxed silicon and the silicon germanium.
3. The device of claim 1 , the insulating material comprising oxide.
4. The device of claim 1 , in which a given thyristor-based memory element comprises a thyristor fabricated in the first region.
5. The device of claim 4 , in which the given thyristor-based memory element further comprises an access device formed in the first region.
6. The device of claim 5 , the access device comprising a MOSFET.
7. The device of claim 6 , further comprising combinational logic fabricated in the second region.
8. The device of claim 7 , in which the combinational logic comprises at least one of a decoder, sense circuitry, read/write circuit, buffer, multiplexer and voltage reference at least partly fabricated in the second region.
9. The device of claim 8 , in which the logic comprises a MOSFET incorporating a portion of the strained silicon for its channel region.
10. The device of claim 1 , the first region comprising a thyristor and the second region comprising an access device operable to provide gatable access to the thyristor.
11. The device of claim 10 , further comprising isolation material disposed in a trench defined in part between respective sidewalls of the second region and the first region.
12. The device of claim 1 , in which a given thyristor-based memory element comprises:
a thyristor defined at least in part in the first region; and
an access device operable to enable retentive access of the thyristor and defined at least in part in the second region.
13. The device of claim 12 , further comprising an interconnect to electrically couple the thyristor and the access device in series relationship.
14. The device claim 13 , the access device comprising a MOSFET having a gate electrode operable under bias to effect a conductive channel in the body region between the source and drain regions; the strained silicon comprising at least part of the body region of the MOSFET for the inverted channel.
15. The device of claim 1 , the silicon germanium comprising relaxed silicon germanium.
16. The device of claim 15 , the silicon germanium further comprising graded silicon germanium contiguous with and disposed beneath the relaxed silicon germanium.
17. The device of claim 15 , the relaxed silicon germanium comprising at least 10 percent germanium by molar fraction.
18. The device of claim 15 , the relaxed silicon germanium comprising less than 30 percent germanium by molar fraction.
19. The device of claim 1 , further comprising isolation material disposed in a trench defined at least in part by sidewalls of the first region and the second region.