Method for forming memory cell transistor
A method for forming a memory cell transistor is disclosed which includes providing a substrate, forming a trench structure in the substrate, depositing a conductive substance on the surface of the substrate to form a conductive member inside the trench structure, forming one or more dielectric layers on the surface of the substrate, forming one or more first conductive layers on top of the dielectric layers, and etching the first conductive layers and the dielectric layers to form a hole structure extending through the first conductive and the dielectric layers, reaching to the substrate surface. The formed memory cell transistor thus comprises a hole structure which is formed from the surface of the top first conductive layer, extending downwards through the first conductive layers and the dielectric layers, and reaching the substrate surface. One or more second conductive layers may be formed on top of the first conductive layers, with the second conductive layer material filling the hole structure.
1. A memory cell transistor structure, comprising:
a substrate, said substrate comprising a trench structure, said trench structure comprising an oxide layer formed on an inner surface of said trench structure and a conductive member which at least partially occupies the inner space of said trench structure;
one or more dielectric layers formed on top of said substrate, said dielectric layers covering said trench structure and said conductive member therein;
one or more first conductive layers formed on top of said dielectric layers; and
one or more second conductive layers formed on top of said first conductive layers, wherein material of said one or more second conductive layers are different to material of said one or more first conductive layers;
wherein said first and second conductive layers function as a bit line associated with said memory cell transistor structure, and said bit line is composed of said first and second conductive layers; a hole structure is formed from a top surface of said first conductive layer, extending only through said first conductive layer and said dielectric layers, and reaching a surface of said substrate, but said hole structure does not extend through said bit line completely; and wherein said material of said second conductive layer fills said hole structure.
2. The memory cell transistor structure of claim 1 , wherein said dielectric layers and said first and second conductive layers are defined to extend along a direction at an angle with a direction of said trench structure, said angle being from about zero to ninety degrees.
3. The memory cell transistor structure of claim 1 , wherein said oxide layer functions as a gate dielectric for said memory cell transistor structure.
4. The memory cell transistor structure of claim 1 , wherein said conductive member functions as a gate electrode of said memory cell transistor and a word line associated with said memory cell transistor structure.
5. The memory cell transistor structure of claim 1 , wherein said filled hole structure functions as a bit line contact plug for said memory cell transistor structure.
6. The memory cell transistor structure of claim 1 , wherein said first conductive layer is formed from a substance comprising polysilicon.
7. The memory cell transistor structure of claim 1 , wherein said second conductive layer is formed from a substance comprising titanium, titanium nitride, tungsten, or any combination thereof.