Semiconductor memory device and fabrication method thereof
A method for fabricating a semiconductor memory device is disclosed. A substrate having a main surface is provided. A memory gate is formed on the main surface of the substrate. The memory has a first sidewall and a second sidewall opposite to the first sidewall. A control gate is formed in proximity to the memory gate. The control gate has a third sidewall directly facing the second sidewall, and a fourth sidewall opposite to the third sidewall. A gap is formed between the second sidewall of the memory gate and the third sidewall of the control gate. A first single spacer structure is formed on the first sidewall of the memory gate and a second single spacer structure on the fourth sidewall of the control gate. A gap-filling layer is formed to fill up the gap.
1. A method for fabricating a semiconductor memory device, comprising:
providing a substrate having a main surface;
forming a memory gate on the main surface of the substrate, wherein the memory has a first sidewall and a second sidewall opposite to the first sidewall;
forming a control gate in proximity to the memory gate, wherein the control gate has a third sidewall directly facing the second sidewall, and a fourth sidewall opposite to the third sidewall;
forming a gap between the second sidewall of the memory gate and the third sidewall of the control gate;
forming a first single spacer structure on the first sidewall of the memory gate and a second single spacer structure on the fourth sidewall of the control gate; and
forming a gap-filling layer to fill up the gap.
2. The method for fabricating a semiconductor memory device according to claim 1 , wherein the first single spacer structure, the second single spacer structure and the gap filling layer all consist of only one layer of dielectric material.
3. The method for fabricating a semiconductor memory device according to claim 2 , wherein said only one layer of dielectric material is a silicon nitride layer.
4. The method for fabricating a semiconductor memory device according to claim 1 , wherein the first single spacer structure is in direct contact with the first sidewall and the main surface of the substrate, the second single spacer structure is in direct contact with the fourth sidewall and the main surface of the substrate.
5. The method for fabricating a semiconductor memory device according to claim 1 , wherein the gap filling layer is in direct contact with the second sidewall and the third sidewall.
6. The method for fabricating a semiconductor memory device according to claim 1 , wherein the gap filling layer has a top surface that is flush with a top surface of the memory gate and a top surface of the control gate.
7. The method for fabricating a semiconductor memory device according to claim 1 further comprising:
forming a first source/drain doping region in the main surface of the substrate and adjacent to the first single spacer structure; and
forming a second source/drain doping region in the main surface of the substrate and adjacent to the second single spacer structure.
8. The method for fabricating a semiconductor memory device according to claim 1 further comprising:
forming a recessed region at a bottom of the gap.
9. The method for fabricating a semiconductor memory device according to claim 1 , wherein the memory gate comprises an oxide-nitride-oxide (ONO) film, a polysilicon layer on the ONO film, and a cap layer on the polysilicon layer.
10. The method for fabricating a semiconductor memory device according to claim 1 , wherein the control gate comprises a polysilicon layer.