Dual work function recessed access device and methods of forming
First Claim
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1. A recessed access device, comprising:
- semiconductor material having at least one trench therein;
a gate dielectric over a surface of the at least one trench;
a first gate material lining in a bottom portion of the at least one trench;
the first gate material lining comprising a radially outer surface in the bottom portion of the trench, a radially inner surface in the bottom portion of the trench that is parallel with most of the radially outer surface, and a pair of top surfaces within the bottom portion of the trench intersecting each of the radially outer and inner surfaces of the first gate material lining;
the radially outer and inner surfaces each extending continuously between the pair of top surfaces; and
a second gate material within the at least one trench transversally over a sidewall of the radially inner surface of the first gate material lining, the second gate material being of different composition from composition of the first gate material, the second gate material projecting elevationally outward within the at least one trench relative to the pair of to surfaces of the first gate material lining.
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Abstract
A recessed access device having a gate electrode formed of two or more gate materials having different work functions may reduce the gate-induced drain leakage current losses from the recessed access device. The gate electrode may include a first gate material having a high work function disposed in a bottom portion of the recessed access device and a second gate material having a lower work function disposed over the first gate material and in an upper portion of the recessed access device.
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Citations
22 Claims
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1. A recessed access device, comprising:
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semiconductor material having at least one trench therein; a gate dielectric over a surface of the at least one trench; a first gate material lining in a bottom portion of the at least one trench;
the first gate material lining comprising a radially outer surface in the bottom portion of the trench, a radially inner surface in the bottom portion of the trench that is parallel with most of the radially outer surface, and a pair of top surfaces within the bottom portion of the trench intersecting each of the radially outer and inner surfaces of the first gate material lining;
the radially outer and inner surfaces each extending continuously between the pair of top surfaces; anda second gate material within the at least one trench transversally over a sidewall of the radially inner surface of the first gate material lining, the second gate material being of different composition from composition of the first gate material, the second gate material projecting elevationally outward within the at least one trench relative to the pair of to surfaces of the first gate material lining. - View Dependent Claims (2, 3, 4, 5)
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6. A recessed access device, comprising:
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semiconductor material having at least one trench therein; a gate dielectric over a surface of the at least one trench; a first gate material lining in a bottom portion of the at least one trench; a second gate material within the at least one trench over the first gate material lining, the second gate material being of different composition from composition of the first gate material, the second gate material projecting outwardly within the at least one trench relative to the first gate material lining that is in the bottom portion of the at least one trench; and the first gate material lining having multiple spaced and separated elevationally outermost top surfaces, the second gate material being elevationally over said multiple spaced and separated elevationally outermost top surfaces. - View Dependent Claims (7, 8, 9)
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10. A recessed access device, comprising:
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semiconductor material having at least one trench therein; a gate dielectric over a surface of the at least one trench; a first gate material lining over only a lowest-most portion of the at least one trench; a second gate material within the at least one trench over the first gate material lining, the second gate material being of different composition from composition of the first gate material, the second gate material projecting outwardly within the at least one trench relative to the first gate material lining that is over only said lowest-most portion of the at least one trench; and a third gate material within the at least one trench and over the second gate material, the third gate material being of different composition from composition of the first gate material and of different composition from composition of the second gate material.
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11. A recessed access device, comprising:
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semiconductor material having an elevationally outermost surface and having at least one trench therein; a gate dielectric over a surface of the at least one trench; a first gate material over at least a portion of the gate dielectric in a bottom portion of the at least one trench and having an elevationally outermost surface within the at least one trench that is elevationally inward of the elevationally outermost surface of the semiconductor material; a second gate material over the first gate material in at least a portion of the at least one trench, the second gate material being of different composition from composition of the first gate material; and a third gate material in at least a portion of the at least one trench over the first gate material and the second gate material, the third gate material contacting the at least a portion of the gate dielectric in the at least one trench, the third gate material being of different composition from composition of the first gate material and of different composition from composition of the second gate material. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A recessed access device, comprising:
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semiconductor material having at least one trench therein; a gate dielectric over a surface of the at least one trench, the gate dielectric comprising an arcuate outer surface in a bottom portion of the at least one trench; a first gate material over at least a portion of the gate dielectric in the bottom portion of the at least one trench, the first gate material comprising an arcuate outer surface in a bottom portion of the at least one trench; and a second gate material over the arcuate outer surface of the first gate material in at least a portion of the at least one trench, the second gate material being of different composition from composition of the first gate material, the second gate material having an upper neck portion within the at least one trench and the second gate material having a lower shouldered portion within the at least one trench in a cross section transverse the at least one trench, the upper neck portion being laterally centered relative to the shouldered portion, the upper neck portion in including a portion within the at least one trench that projects elevationally outward of all first gate material that is within the at least one trench. - View Dependent Claims (19, 20, 21, 22)
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Specification