1. A method of fabricating a semiconductor device, comprising:
forming a plurality of stacked structures on a substrate;
forming a first dielectric layer to cover the stacked structures, wherein the first dielectric layer has a plurality of overhangs, the overhangs wrap top portions of the stacked structures;
performing a dry conformable etching process to conformably remove the first dielectric layer until a portion of the first dielectric layer located outside of the overhangs is completely removed; and
forming a second dielectric layer on the stacked structures, wherein the second dielectric layer connects the adjacent overhangs to form an air gap between the stacked structures.
2. The method of fabricating the semiconductor device of claim 1, further comprising forming a liner layer to cover the stacked structures after the stacked structures are formed.
3. The method of fabricating the semiconductor device of claim 2, wherein an etching rate of the liner layer is smaller than an etching rate of the first dielectric layer during the dry conformable etching process.
4. The method of fabricating the semiconductor device of claim 1, wherein the dry conformable etching process comprises an isotropic etching process.
5. The method of fabricating the semiconductor device of claim 4, wherein the dry conformable etching process comprises a non-plasma etching process or a plasma etching process.
6. The method of fabricating the semiconductor device of claim 1, wherein the dry conformable etching process comprises a gas etching process.
7. The method of fabricating the semiconductor device of claim 6, wherein the dry conformable etching process is adapted for a line width of less than or equal to 50 nanometers.
8. The method of fabricating the semiconductor device of claim 1, wherein a ratio of a sectional area of the air gap to a sectional area of a space between the stacked structures is higher than 70% and less than or equal to 90%.
9. The method of fabricating the semiconductor device of claim 1, wherein when the semiconductor device is a non-volatile memory, each of the stacked structures successively comprises a tunneling dielectric layer, a floating gate, an inter-gate dielectric layer and a control gate from bottom to top.
10. The method of fabricating the semiconductor device of claim 9, wherein the dry conformable etching process comprises: removing a portion of the first dielectric layer located below or equal to a height of a top portion of each of the control gates.
11. The method of fabricating the semiconductor device of claim 9, wherein a lower width of the air gap is larger than or equal to an upper width of the air gap between the floating gates.
12. The method of fabricating the semiconductor device of claim 9, wherein each of the stacked structures further comprises a conductor layer, disposed on each of the control gates.
13. The method of fabricating the semiconductor device of claim 1, wherein each of the stacked structures further comprises a cap layer, the cap layer is an uppermost layer of the stacked structure.
14. The method of fabricating the semiconductor device of claim 13, wherein the dry conformable etching process comprises removing a portion of the first dielectric layer located below or equal to a height of the bottom portion of the cap layer.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A communication network operable to provide online charging for a session of a dual mode device that is transferred from a first network domain to a second network domain, the communication network comprising:
at least one network element in the second network domain that is operable to receive a handover charging identifier that is assigned for online charging for the session over the first network domain and the second network domain wherein the session was handed over from the first network domain to the second network domain, to store the handover charging identifier, to identify a triggering event for charging during the session over the second network domain, to generate an online charging request for the session and insert the handover charging identifier in the online charging request, and to transmit the online charging request to an online charging system.
2. The communication network of claim 1 further comprising the online charging system that is operable to:
receive at least one online charging request from the at least one network element in the second network domain;
process the at least one online charging request to identify the handover charging identifier;
correlate the at least one online charging request with other online charging requests for the session over the first network domain or the second network domain to determine a charging rate;
grant a credit quota based on the charging rate;
generate an online charging response that includes the credit quota; and
transmit the online charging response to the at least one network element in the second network domain.
3. The communication network of claim 1 wherein the online charging system is operable to:
identify the transfer of the session from the first network domain to the second network domain;
determine whether to have at least one network element in the first network domain surrender unused credits granted to the at least one network element in the first network domain while the session was in the first network domain;
transmit a credit return request to the at least one network element in the first network domain responsive to a determination to surrender the unused credits;
receive at least one online charging request from the at least one network element in the first network domain that includes the unused credits; and
return the unused credits to an account of the user of the dual mode device.
4. The communication network of claim 1 further comprising a handover application server operable to:
receive a session initiation request from the at least one network element in the second network domain;
identify the handover charging identifier for the session; and
distribute the handover charging identifier to the at least one network element in the second network domain indicating the handover charging identifier to be used in online charging requests to the online charging system.
5. The communication network of claim 4 wherein the handover application server is further operable to:
generate an online charging request for the session;
insert the handover charging identifier in the online charging request; and
transmit the online charging request to the online charging system.
6. The communication network of claim 1 wherein the at least one network element in the second network domain is further operable to:
insert a handover indicator in the at least one online charging request indicating the transfer of the session from the first network domain to the second network domain.
7. The communication network of claim 6 wherein the at least one network element in the second network domain is further operable to:
identify a timestamp of the transfer of the session from the first network domain to the second network domain; and
insert the timestamp in the at least one online charging request.
8. The communication network of claim 7 wherein the at least one online charging request comprises a Diameter charging request, and the at least one network element in the second network domain is further operable to:
insert the handover charging identifier in a first new attribute value pair (AVP) in the Diameter charging request;
insert the handover indicator in a second new attribute value pair (AVP) in the Diameter charging request; and
insert the timestamp in a third new attribute value pair (AVP) in the Diameter charging request.
9. A method of providing online charging for a session of a dual mode device that is transferred from a first network domain to a second network domain, the method comprising:
receiving a handover charging identifier in at least one network element in the second network domain, wherein the handover charging identifier is for online charging for the session over the first network domain and the second network domain;
storing the handover charging identifier in the at least one network element in the second network domain;
identifying a triggering event for charging in the at least one network element in the second network domain during the session over the second network domain, generating an online charging request for the session and inserting the handover charging identifier in the online charging request; and
transmitting the online charging request to an online charging system.
10. The method of claim 9 further comprising:
receiving the at least one online charging request in the online charging system from the at least one network element in the second network domain;
processing the at least one online charging request in the online charging system to identify the handover charging identifier;
correlating the at least one online charging request with other online charging requests for the session over the first network domain or the second network domain to determine a charging rate;
granting a credit quota based on the charging rate;
generating an online charging response that includes the credit quota; and
transmitting the online charging response from the online charging system to the at least one network element in the second network domain.
11. The method of claim 10 further comprising:
identifying the transfer of the session from the first network domain to the second network domain in the online charging system;
determining whether to have at least one network element in the first network domain surrender unused credits granted to the at least one network element in the first network domain while the session was in the first network domain;
transmitting a credit return request to the at least one network element in the first network domain responsive to a determination to surrender the unused credits;
receiving at least one online charging request from the at least one network element in the first network domain that includes the unused credits; and
returning the unused credits to an account of the user of the dual mode device.
12. The method of claim 9 further comprising:
receiving a session initiation request in a handover application server from the at least one network element in the second network domain;
identifying the handover charging identifier for the session; and
distributing the handover charging identifier to the at least one network element in the second network domain indicating the handover charging identifier to be used in online charging requests to the online charging system.
13. The method of claim 12 further comprising:
generating an online charging request for the session in the handover application server;
inserting the handover charging identifier in the online charging request; and
transmitting the online charging request to the online charging system.
14. The method of claim 9 further comprising:
inserting a handover indicator in the at least one online charging request indicating the transfer of the session from the first network domain to the second network domain.
15. The method of claim 14 further comprising:
identifying a timestamp of the transfer of the session from the first network domain to the second network domain; and
inserting the timestamp in the at least one online charging request.
16. The method of claim 15 wherein the at least one online charging request comprises a Diameter charging request, and the method further comprises:
inserting the handover charging identifier in a first new attribute value pair (AVP) in the Diameter charging request;
inserting the handover indicator in a second new attribute value pair (AVP) in the Diameter charging request; and
inserting the timestamp in a third new attribute value pair (AVP) in the Diameter charging request.
17. A method of operating a handover application server to provide online charging for a session of a dual mode device that is transferred from a first network domain to a second network domain, the method comprising:
receiving a session initiation request from at least one network element that is serving the session in the second network domain which was handed over from the first network domain
identifying a handover charging identifier for the session; and
distributing the handover charging identifier to the at least one network element in the second network domain indicating the handover charging identifier to be used in online charging requests to an online charging system.
18. The method of claim 17 further comprising:
receiving a session initiation request from at least one network element that is serving the session in the first network domain prior to the session being transferred to the second network domain;
identifying the handover charging identifier for the session; and
distributing the handover charging identifier to the at least one network element in the first network domain indicating the handover charging identifier to be used in online charging requests to the online charging system.
19. The method of claim 18 further comprising:
generating an online charging request for the session in the handover application server;
inserting the handover charging identifier in the online charging request; and
transmitting the online charging request to the online charging system.
20. The method of claim 19 wherein the online charging request comprises a Diameter charging request, and the method further comprises:
inserting the handover charging identifier in a new attribute value pair (AVP) in the Diameter charging request.