Flash memories and methods of fabricating the same
View Patent ↗The present disclosure relates to a flash memory including a common source line having a predetermined width formed on a semiconductor substrate, a common source in the semiconductor substrate below the common source line, and a couple of floating gates having a predetermined width formed on both outer side walls of the common source line. The flash memory may also include a couple of tunneling oxide layers formed between the floating gate and the common source line, and between the floating gate and the semiconductor substrate, a couple of dielectric layers formed on each of the couple of floating gates, and a couple of control gates formed on each of the couple of dielectric layers. Further, the flash memory may include a couple of drains formed in the semiconductor substrate by injecting impurity ions in using the control gate and the common source line as a mask.
1. A flash memory comprising:
a common source line having a first predetermined width, on a semiconductor substrate;
a common source in the semiconductor substrate below the common source line;
first and second floating gates having a second predetermined width and a height substantially equal to that of the common source line, on outer side walls of the common source line;
first tunneling oxide layers between the first floating gate and the semiconductor substrate;
a second tunneling oxide layer between to second floating gate and the semiconductor substrate;
first and second dielectric layers, each comprising a first oxide layer, a nitride layer, and a second oxide layer, respectively on top and side surfaces of the first and second floating gates and over the semiconductor substrate outside the first and second floating gates;
first and second control gates respectively on the first and second dielectric layers, including over the semiconductor substrate outside the first and second floating gates such that the first and second control gates each have a step; and
first and second drains in the semiconductor substrate outside the control gate and the common source line.
2. The flash memory as defined by claim 1 , wherein the common source line comprises impurity-doped polycrystalline silicon.
3. The flash memory as defined by claim 1 , wherein the first tunneling oxide layer is further between the first floating gate and the common source line.
4. The flash memory as defined by claim 3 , wherein the first dielectric layer covers the first floating gate and the first tunneling oxide layer.
5. The method as defined by claim 1 , wherein the first and second control gates have a predetermined width.
6. The flash memory as defined by claim 1 , wherein each of the first and second drains is independently controlled.
7. The flash memory as defined by claim 3 , wherein the second tunneling oxide layer is further between the second floating gate and the common source line.
8. The flash memory as defined by claim 3 , wherein the first tunneling oxide layer is further on the semiconductor substrate outside of the first floating gate.
9. The flash memory as defined by claim 7 , wherein the second tunneling oxide layer is further on the semiconductor substrate outside of the floating gate.
10. The flash memory as defined by claim 4 , wherein the second dielectric layer covers the second floating gate and the second tunneling oxide layer.
11. The flash memory as defined by claim 5 , wherein the first and second dielectric layers have a predetermined width.
12. The flash memory as defined by claim 11 , wherein the predetermined width of the first and second dielectric layers is substantially the same as the first and second control gates.
13. The flash memory as defined by claim 1 , farther comprising a third tunneling oxide between the first floating gate and the common source line.
14. The flush memory as defined by claim 13 , further comprising a fourth tunneling oxide between the second floating gate and the common source line.
15. The flash memory as defined by claim 1 , wherein the first and second control gates have an inner sidewall over the first and second floating gates, respectively.