Method of manufacturing a flash memory device
A method of manufacturing a flash memory device is disclosed. The method includes the steps of providing a semiconductor substrate in which a cell region and a select transistor region are defined, etching the semiconductor substrate in the select transistor region so that there is a first step between the cell region and the select transistor region, forming a cell gate in the cell region, and forming a transistor in the select transistor region.
1. A method of manufacturing a flash memory device, comprising the steps of:
providing a semiconductor substrate in which a cell region and a select transistor region are defined;
etching the semiconductor substrate in the select transistor region to form a first step between the cell region and the select transistor region; and,
forming a cell gate in the cell region, and forming a transistor in the select transistor region.
2. The method of claim 1 , wherein a width of the etched select transistor region 4 to 6 times larger than that of the transistor.
3. The method of claim 1 , wherein the first step has a height ranging from 300 Å to 1000 Å.
4. The method of claim 1 , wherein the first step has a slope between the transistor and the cell gate adjacent to the transistor.
5. The method of claim 4 , comprising controlling the angle of the slope depending on a polymer formation method and a corresponding amount of polymer used when etching the semiconductor substrate.
6. The method of claim 1 , wherein the cell gate has a stacked structure comprising a floating gate, a dielectric layer and a control gate.
7. The method of claim 6 , comprising forming the floating gate from a polysilicon layer by in-situ implanting a P or B dopant into a source gas.
8. The method of claim 7 , wherein the source gas is selected from the group consisting of SiH 4 , Si 2 H 6 , and SiH 2 Cl 2 .
9. The method of claim 6 , comprising forming the cell gate in the cell region and the transistor in the select transistor region at the same time.
10. The method of claim 1 , further comprising, after forming the cell gate and the transistor, the steps of:
forming spacers on sidewalls of the cell gate and the transistor;
forming a first insulating layer over the semiconductor substrate including the spacers, the cell gate and the transistor;
etching the first insulating layer to form a source contact plug;
forming a second insulating layer on the first insulating layer and the source contact plug; and,
etching the second insulating layer and the first insulating layer to form a drain contact plug.
11. The method of claim 10 , further comprising forming an insulating layer over the semiconductor substrate including the spacers, the cell gate and the transistor before the first insulating layer is formed.
12. The method of claim 10 , wherein the formation of the first insulating layer and the formation of the second insulating layer has a second step between the select transistor region and the cell region.