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US 8,008,144 B2Granted
Dual work function recessed access device and methods of forming
AssigneeMicron Technology, Inc.
InventorsVenkatesan Ananthan, Sanh D. Tang
Life of this patent
Estimating the term…
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.
Claims14
A method of forming a recessed access device, comprising:
- providing a semiconductor substrate having at least one trench formed therein;
- forming a gate-oxide layer over a surface of the at least one trench;
- forming a layer of substantially uniform thickness of a first gate material having a first work function over at least a portion of the gate-oxide layer in a bottom portion of the at least one trench, the first gate material comprising material selected from the group consisting of p-type doped polysilicon, titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), ruthenium (Ru), molybdenum nitride (MoN), TaN/TiN, WN/TiN, p-type polysilicon/TiN, and combinations thereof;
- removing at least a portion of the layer of first gate material to expose at least a portion of the gate-oxide layer in the at least one trench;
- forming a second gate material having a second work function over the first gate material in at least a portion of the at least one trench, wherein the second work function is lower than the first work function;
- and
- forming a third gate material over the first gate material and the second gate material, wherein the third gate material contacts the at least a portion of the gate-oxide layer in the at least one trench exposed by removing at least a portion of the layer of first gate material.
4 more elements
A method of forming a recessed access device, comprising:
- providing semiconductor material having at least one trench formed therein;
- forming 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;
- forming a first gate material having a first work function over at least a portion of the gate dielectric in the bottom portion of the at least one trench, the first gate material being formed to be U-shaped in a lateral cross section;
- and
- forming a second gate material having a second work function over the first gate material in at least a portion of the at least one trench and into a lateral center of the U of the U-shaped cross section first gate material, wherein the second work function is lower than the first work function, the second gate material being formed to have an upper neck portion within the trench and a lower shouldered portion within the trench in the lateral cross section, the upper neck portion being laterally centered relative to the shouldered portion.
2 more elements
A method of forming a recessed access device, comprising:
- providing a semiconductor substrate having at least one trench formed therein;
- lining the trench with gate dielectric;
- lining the trench with a first gate material over the gate dielectric, the first gate material having a first work function;
- overfilling the trench with a second gate material having a second work function which is lower than the first work function;
- removing the second gate material to expose the first gate material which lines the trench;
- and
- etching the exposed first gate material to recess it within the trench and leave second gate material within the trench projecting outwardly relative to the recessed first gate material.
4 more elements
A method of forming a recessed access device, comprising:
- providing a semiconductor substrate having at least one trench formed therein;
- forming a gate dielectric layer over a surface of the at least one trench;
- forming a first gate material having a first work function over at least a portion of the gate dielectric layer in a bottom portion of the at least one trench;
- removing at least a portion of the layer of first gate material to expose at least a portion of the gate dielectric layer in the at least one trench;
- forming a second gate material having a second work function over the first gate material in at least a portion of the at least one trench, wherein the second work function is lower than the first work function;
- and
- forming a third gate material over the first gate material and the second gate material, wherein the third gate material contacts the at least a portion of the gate dielectric layer in the at least one trench exposed by removing at least a portion of the layer of first gate material.
4 more elements
A method of forming a recessed access device, comprising:
- providing semiconductor material having at least one trench formed therein;
- forming 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;
- forming a first gate material having a first work function 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
- forming a second gate material having a second work function over the arcuate outer surface of the first gate material in at least a portion of the at least one trench, wherein the second work function is lower than the first work function, the second gate material being formed to have an upper neck portion within the trench and a lower shouldered portion within the trench in the lateral cross section, the upper neck portion being laterally centered relative to the shouldered portion.
2 more elements
Dependencies are inferred from the claim text.