1. A method comprising:
determining, by a radio access network (RAN), a metric indicative of a prevalence of wireless communication devices (WCDs) of a first type that are served by the RAN, wherein WCDs of a second type are also served by the RAN, wherein WCDs of the first type are configured to communicate with the RAN using a first air-interface or a second air-interface, wherein WCDs of the second type are configured to communicate using the second air-interface and not the first air-interface, and wherein the RAN is configured to engage in a first extent of substantially simultaneous communication with WCDs of either the first type or the second type when using the second air-interface;
comparing the metric to a threshold WCD prevalence;
based on the comparison of the metric to the threshold WCD prevalence, selecting a second extent of substantially simultaneous communication to engage in with WCDs of either the first type or the second type when using the second air-interface;
receiving, by the RAN, a call setup request related to a particular WCD; and
in response to receiving the call setup request, selecting at most the second extent of wireless coverage areas for the particular WCD to engage in communication with the RAN via the second air-interface.
2. The method of claim 1 further comprising:
if the selected wireless coverage areas consist of one wireless coverage area, communicating with the particular WCD via the one wireless coverage area; and
if the selected wireless coverage areas consist of more than one wireless coverage area, communicating with the particular WCD substantially simultaneously via each selected wireless coverage area.
3. The method of claim 1, wherein communicating with the particular WCD substantially simultaneously via each selected wireless coverage area comprises:
during establishment of a call in which the particular WCD participates, the RAN transmitting respective channel assignment messages to the particular WCD via each selected wireless coverage area.
4. The method of claim 1, wherein communicating with the particular WCD substantially simultaneously via each selected wireless coverage area comprises:
during establishment of a call in which the particular WCD participates, the RAN assigning, to the particular WCD, respective traffic channels from each selected wireless coverage area; and
during an initial portion of the call, the RAN exchanging bearer traffic with the particular WCD via each of the assigned traffic channels.
5. The method of claim 4, wherein the RAN transmits and receives identical copies of the same bearer traffic via each of the assigned traffic channels.
6. The method of claim 1, wherein the first air-interface operates in accordance with Long-Term Evolution (LTE), and wherein the second air-interface operates in accordance with Code Division Multiple Access (CDMA).
7. The method of claim 6, wherein the RAN is a CDMA RAN.
8. The method of claim 6, wherein the RAN comprises:
a CDMA component configured to communicate using the second air-interface; and
an LTE component configured to communicate using the first air-interface.
9. The method of claim 1, wherein the metric comprises a number of WCDs of the first type served by the RAN, and wherein comparing the metric to the threshold WCD prevalence comprises determining that the number of WCDs of the first type exceeds the threshold WCD prevalence.
10. The method of claim 1, wherein the metric comprises a percentage of WCDs of the first type served by the RAN out of all WCDs served by the RAN, and wherein comparing the metric to the threshold WCD prevalence comprises determining that the percentage of WCDs of the first type exceeds the threshold WCD prevalence.
11. The method of claim 1, wherein if the metric meets the threshold WCD prevalence, the second extent is selected to be less than the first extent, and wherein if the metric does not meet the threshold WCD prevalence, the second extent is selected to be greater than the first extent.
12. A non-transitory computer-readable medium having stored thereon program instructions that, upon execution by a radio access network (RAN) device of a RAN, cause the RAN device to perform functions comprising:
determining a metric indicative of a prevalence of wireless communication devices (WCDs) of a first type that are served by the RAN, wherein WCDs of a second type are also served by the RAN, wherein WCDs of the first type are configured to communicate with the RAN using a first air-interface or a second air-interface, wherein WCDs of the second type are configured to communicate using the second air-interface and not the first air-interface, and wherein the RAN device is configured to engage in a first extent of substantially simultaneous communication with WCDs of either the first type or the second type when using the second air-interface;
comparing the metric to a threshold WCD prevalence;
based on the comparison of the metric to the threshold WCD prevalence, selecting a second extent of substantially simultaneous communication to engage in with WCDs of either the first type or the second type when using the second air-interface;
receiving a call setup request related to a particular WCD; and
in response to receiving the call setup request, assigning at most the second extent of wireless coverage areas for the particular WCD to engage in communication with the RAN device using the second air-interface.
13. The non-transitory computer-readable medium of claim 12, wherein the functions further comprise:
if the selected wireless coverage areas consist of one wireless coverage area, communicating with the particular WCD via the one wireless coverage area; and
if the selected wireless coverage areas consist of more than one wireless coverage area, communicating with the particular WCD substantially simultaneously via each selected wireless coverage area.
14. The non-transitory computer-readable medium of claim 12, wherein the function of communicating with the particular WCD substantially simultaneously via each selected wireless coverage area comprises:
during establishment of a call in which the particular WCD participates, transmitting respective channel assignment messages to the particular WCD via each selected wireless coverage area.
15. The non-transitory computer-readable medium of claim 12, wherein the function of communicating with the particular WCD substantially simultaneously via each selected wireless coverage area comprises:
during establishment of a call in which the particular WCD participates, assigning, to the particular WCD, respective traffic channels from each selected wireless coverage area; and
during an initial portion of the call, exchanging bearer traffic with the particular WCD via each of the assigned traffic channels.
16. The non-transitory computer-readable medium of claim 15, wherein the RAN device transmits and receives identical copies of the same bearer traffic via each of the assigned traffic channels.
17. A radio access network (RAN) device of a RAN comprising:
a processor;
a data storage; and
program instructions, stored in the data storage and executable by the processor, that cause the RAN device to:
determine a metric indicative of a prevalence of wireless communication devices (WCDs) of a first type that are served by the RAN, wherein WCDs of a second type are also served by the RAN, wherein WCDs of the first type are configured to communicate with the RAN device using a first air-interface or a second air-interface, wherein WCDs of the second type are configured to communicate using the second air-interface and not the first air-interface, and wherein the RAN device is configured to engage in a first extent of substantially simultaneous communication with WCDs of either the first type or the second type when using the second air-interface;
compare the metric to a threshold WCD prevalence;
based on the comparison of the metric to the threshold WCD prevalence, select a second extent of substantially simultaneous communication to engage in with WCDs of either the first type or the second type when using the second air-interface;
receive a call setup request related to a particular WCD; and
in response to receiving the call setup request, select at most the second extent of wireless coverage areas for the particular WCD to engage in communication with the RAN device using the second air-interface.
18. The RAN device of claim 17, wherein the program instructions are further executable by the processor to cause the RAN device to:
communicate, if the selected wireless coverage areas consist of one wireless coverage area, with the particular WCD via the one wireless coverage area; and
communicate, if the selected wireless coverage areas consist of more than one wireless coverage area, with the particular WCD substantially simultaneously via each selected wireless coverage area.
19. The RAN device of claim 18, wherein, to communicate with the particular WCD substantially simultaneously via each selected wireless coverage area, the program instructions are further executable by the processor to cause the RAN device to:
transmit, during establishment of a call in which the particular WCD participates, respective channel assignment messages to the particular WCD via each selected wireless coverage area
20. The RAN device of claim 19, wherein, to communicate with the particular WCD substantially simultaneously via each selected wireless coverage area, the program instructions are further executable by the processor to cause the RAN device to:
assign, during establishment of a call in which the particular WCD participates, to the particular WCD, respective traffic channels from each selected wireless coverage area; and
exchange, during an initial portion of the call, bearer traffic with the particular WCD via each of the assigned traffic channels.
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 semiconductor device manufacturing method comprising:
forming a gate interconnect both in a first region and a second region of a semiconductor substrate, forming in the first region a first transistor including a first gate electrode which is a part of the gate interconnect, and forming in the second region a second transistor including a second gate electrode which is another part of the gate interconnect;
forming over the semiconductor substrate a first stress film so as to cover the first transistor and the second transistor;
forming a first etching stopper film over the first stress film;
forming over the first etching stopper film a second etching stopper film whose etching characteristic is different from an etching characteristic of the first etching stopper film;
forming a first mask layer covering the first region and exposing the second region;
removing the second etching stopper film in the second region with the first mask layer as a mask and the first etching stopper film as the stopper, and isotropically etching the second etching stopper film located below the first mask layer;
etching off the first etching stopper film and the first stress film in the second region with the first mask layer as a mask;
forming over the semiconductor substrate the second stress film whose etching characteristic is different from an etching characteristic of the second etching stopper film, covering the second transistor, the first stress film, the first etching stopper film and the second etching stopper film;
forming over the second stress film a second mask layer covering the second region, an end face of the second mask layer on the side of the first region being located over the second etching stopper film;
etching the second stress film with the second mask layer as the mask so that a part of the second stress film overlaps a part of the first stress film and a part of the second etching stopper film;
forming over the semiconductor substrate an insulation film, covering the first stress film, the second stress film, the first etching stopper film and the second etching stopper film;
forming a contact hole through the insulation film, the second stress film, the first etching stopper film and the first stress film down to the gate interconnect at a border between the first region and the second region; and
forming an electrically conductive plug in the contact hole.
2. The semiconductor device manufacturing method according to claim 1, wherein
in the isotropically etching the second etching stopper film located below the first mask layer, the etching is made with an etchant containing hydrofluoric acid.
3. The semiconductor device manufacturing method according to claim 1, wherein
the first stress film is a silicon nitride film;
the second etching stopper film is a silicon oxide film; and
the first etching stopper film is a silicon nitride film whose carbon content ratio is higher than a carbon content ratio of the first stress film.
4. The semiconductor device manufacturing method according to claim 1, wherein
the first stress film is a silicon nitride film;
the second etching stopper film is a silicon oxide film; and
the first etching stopper film is a silicon nitride film whose film density is higher than a film density of the first stress film.
5. The semiconductor device manufacturing method according to claim 1, wherein
the second stress film is a silicon nitride film.
6. The semiconductor device manufacturing method according to claim 1, wherein
the first stress film is a tensile stress film; and
the first etching stopper film and the second stress film are compressive stress films.
7. The semiconductor device manufacturing method according to claim 1, wherein
a film thickness of the first etching stopper film is smaller than a film thickness of the first stress film.
8. The semiconductor device manufacturing method according to claim 7, wherein
the film thickness of the first etching stopper film is \xbd or below of the film thickness of the first stress film.
9. The semiconductor device manufacturing method according to claim 1, wherein
the first transistor is an NMOS transistor; and
the second transistor is a PMOS transistor.
10. A semiconductor device comprising:
a gate interconnect formed both in a first region and a second region of a semiconductor substrate;
a first transistor formed in the first region and including a first gate electrode which is a part of the gate interconnect, and first sourcedrain diffusion layers formed in the semiconductor substrate on both sides of the first gate electrode;
a second transistor formed in the second region and including second gate electrode which is another part of the gate interconnect and second sourcedrain diffusion layers formed in the semiconductor substrate on both side of the second gate electrode;
a first stress film formed over the semiconductor substrate in the first region so as to cover the first transistor;
a first etching stopper film formed over the first stress film;
a second etching stopper film whose etching characteristic is different from an etching characteristic of the first etching stopper film and formed over the first region except a part thereof near the second region;
a second stress film formed over the semiconductor substrate in the second region so as to cover the second transistor, an edge of the second stress film on the side of the first region being overlapped with a part of the first stress film, a part of the first etching stopper film and a part of the second etching stopper film;
an insulation film formed over the semiconductor substrate so as to cover the first stress film, the first etching stopper film, the second etching stopper film and the second stress film; and
an electrically conductive plug buried in a contact hole formed through the insulation film, the second stress film, the first etching stopper film and the first stress film down to the gate interconnect at a border between the first region and the second region,
the end face of the second etching stopper film on the side of the second region receding from the end face of the first stress film on the side of the second region.
11. The semiconductor device according to claim 10, wherein
the first stress film is a silicon nitride film;
the second etching stopper film is a silicon oxide film; and
the first etching stopper film is a silicon nitride film whose carbon content ratio is higher than a carbon content ratio of the first stress film.
12. The semiconductor device according to claim 10, wherein
the first stress film is a silicon nitride film;
the second etching stopper film is a silicon oxide film; and
the first etching stopper film is a silicon nitride film whose film density is higher than a film density of the first stress film.
13. The semiconductor device according to claim 10, wherein
the second stress film is a silicon nitride film.
14. The semiconductor device according to claim 10, wherein
the first stress film is a tensile stress film; and
the first etching stopper film and the second stress film are compressive stress films.
15. The semiconductor device according to claim 10, wherein
a film thickness of the first etching stopper film is smaller than a film thickness of the first stress film.
16. The semiconductor device according to claim 15, wherein
the film thickness of the first etching stopper film is \xbd or below of the film thickness of the first stress film.
17. The semiconductor device according to claim 10, wherein
the first transistor is an NMOS transistor; and
the second transistor is a PMOS transistor.