PHASE-CHANGE MEMORY ELEMENT

1 . A method for fabricating phase-change memory elements, comprising:

forming a first dielectric layer with an opening on an electrode;

forming a heater within the opening to contact with the electrode, wherein the top surface of the heater is higher than that of the first dielectric layer, defining an extended part of the heater with a first width;

subjecting the first dielectric layer and the heater to an etching process to obtain an etched extended part of the heater, wherein the etched extended part has a second width less than the first width;

forming a second dielectric layer covering the etched extended part of the heater;

subjecting the second dielectric layer to a planarization process, exposing the extended part of the heater; and

forming a phase-change material layer on the second dielectric layer and directly in contact with the heater.

2 . The method as claimed in claim 1 , wherein the material of the phase-change material layer comprises chalcogenide.

3 . The method as claimed in claim 1 , wherein the second width is less than the resolution limit of the photolithography process.

4 . The method as claimed in claim 1 , wherein the method for forming the extended part of the heater comprises the following steps:

forming the heater within the opening; and

removing a part of the first dielectric layer, leaving the extended part outside of the top surface of the other part of the first dielectric layer that is not removed.

5 . The method as claimed in claim 1 , wherein the extended part has a length of 10-5000 Å.

6 . The method as claimed in claim 1 , wherein the second width is of 10-1000 Å.

7 . The method as claimed in claim 1 , wherein the heater has an etching rate exceeding that of the first dielectric layer.

8 . The method as claimed in claim 1 , wherein an etching rate of the heater is 50 times larger than that of the first dielectric layer.

9 . The method as claimed in claim 1 , wherein the etching process comprises a wet etching or a dry etching process.

10 . The method as claimed in claim 1 , wherein the planarization process comprises a chemical mechanical polishing process.

11 . The method as claimed in claim 1 , wherein the heater comprises an electrically connected material.

12 . The method as claimed in claim 1 , wherein the heater is made of TaN, W, TiN, or TiW.

13 . A phase-change memory element, comprising:

an electrode;

a first dielectric layer formed on the electrode;

an opening passing through the first dielectric layer, exposing the electrode;

a heater formed in the opening to contact to the electrode, wherein the heater has an extended part outside of the opening;

a second dielectric layer surrounding the heater to expose the top surface of the extended part of the heater; and

a phase-change material layer formed on the second dielectric layer to directly contact to the top surface of the extended part of the heater.

14 . The phase-change memory element as claimed in claim 13 , wherein the material of the phase-change material layer comprises chalcogenide.

15 . The phase-change memory element as claimed in claim 13 , wherein the extended part has a length of 10-5000 Å.

16 . The phase-change memory element as claimed in claim 13 , wherein the top of the extended part has a width of 10-1000 Å.

17 . The phase-change memory element as claimed in claim 13 , wherein the heater is made of TaN, W, TiN, or TiW.

18 . The phase-change memory element as claimed in claim 13 , wherein the top surface of the extended part of the heater is coplanar with the top surface of the second dielectric layer.

19 . The phase-change memory element as claimed in claim 13 , wherein the top surface of the extended part of the heater is higher than the top surface of the second dielectric layer.

20 . The phase-change memory element as claimed in claim 13 , wherein the bottom of the extended part of the heater is lower than the top surface of the first dielectric layer.