Method of fabricating semiconductor transistor devices with asymmetric extension and/or halo implants

1. A method of fabricating semiconductor devices, the method comprising:

fabricating a device structure comprising a semiconductor material and a plurality of gate structures formed overlying the semiconductor material;

creating light dose extension implants in the semiconductor material, using the plurality of gate structures as a first implantation mask, by bombarding the device structure with ions at a non-tilted angle relative to an exposed surface of the semiconductor material;

forming a patterned mask overlying the semiconductor material, the patterned mask being arranged to protect shared drain regions of the semiconductor material and to leave shared source regions of the semiconductor material substantially exposed;

producing heavy dose extension implants in the semiconductor material, using the plurality of gate structures and the patterned mask together as a second implantation mask, by bombarding the device structure with ions at a tilted angle relative to the exposed surface of the semiconductor material, and toward the plurality of gate structures; and

forming halo implants in the semiconductor material, using the second implantation mask, by bombarding the device structure with ions at a second tilted angle relative to the exposed surface of the semiconductor material, and toward the plurality of gate structures.

2. The method of claim 1 , wherein:

each of the plurality of gate structures has sidewalls;

the step of producing heavy dose extension implants comprises bombarding the device structure with ions at a relatively low angle, as measured from the sidewalls; and

the step of forming halo implants comprises bombarding the device structure with ions at a relatively high angle, as measured from the sidewalls.

3. The method of claim 1 , wherein:

the step of creating light dose extension implants comprises implanting a relatively low percentage of a total extension implant dose; and

the step of producing heavy dose extension implants comprises implanting a relatively high percentage of the total extension implant dose.

4. The method of claim 3 , wherein:

the step of creating light dose extension implants comprises implanting between 10% to 40% of the total extension implant dose; and

the step of producing heavy dose extension implants comprises implanting between 60% to 90% of the total extension implant dose.

5. The method of claim 1 , wherein the step of forming the patterned mask comprises completely covering the shared drain regions with mask material.

6. The method of claim 1 , wherein the step of forming the patterned mask comprises completely exposing the shared source regions.

7. The method of claim 1 , wherein each shared source region corresponds to a respective region of the semiconductor material underlying a space between two adjacent ones of the plurality of gate structures.

8. The method of claim 1 , wherein each shared drain region corresponds to a respective region of the semiconductor material underlying a space between two adjacent ones of the plurality of gate structures.

9. A method of fabricating semiconductor devices, the method comprising:

providing a device structure comprising a semiconductor material and a plurality of gate structures formed overlying the semiconductor material;

creating light dose extension implants in the semiconductor material, using the plurality of gate structures as a first implantation mask, by bombarding the device structure with ions at a non-tilted angle relative to a reference surface of the semiconductor material;

forming a patterned mask overlying the semiconductor material, the patterned mask being arranged to protect shared drain regions of the semiconductor material and to leave shared source regions of the semiconductor material substantially exposed;

forming halo implants in the semiconductor material, using the plurality of gate structures and the patterned mask together as a second implantation mask, by bombarding the device structure with ions at a tilted angle relative to the reference surface of the semiconductor material, and toward the plurality of gate structures; and

producing heavy dose extension implants in the semiconductor material, using the second implantation mask, by bombarding the device structure with ions at a second tilted angle relative to the reference surface of the semiconductor material, and toward the plurality of gate structures.

10. The method of claim 9 , wherein:

each of the plurality of gate structures has sidewalls;

the step of forming halo implants comprises bombarding the device structure with ions at a relatively high angle, as measured from the sidewalls; and

the step of producing heavy dose extension implants comprises bombarding the device structure with ions at a relatively low angle, as measured from the sidewalls.

11. The method of claim 9 , wherein:

the step of creating light dose extension implants comprises implanting a relatively low percentage of a total extension implant dose; and

the step of producing heavy dose extension implants comprises implanting a relatively high percentage of the total extension implant dose.

12. A method of fabricating a semiconductor device having adjacent transistor devices that share active regions, the method comprising:

providing a device structure comprising a semiconductor material, a plurality of gate structures formed overlying the semiconductor material, a shared source region of the semiconductor material, which underlies a first space defined between a first gate structure of the plurality of gate structures and a second gate structure of the plurality of gate structures, and a shared drain region of the semiconductor material, which underlies a second space defined between the second gate structure and a third gate structure of the plurality of gate structures, the second gate structure being adjacent to the first gate structure, and the third gate structure being adjacent to the second gate structure;

implanting a relatively light impurity dose into the semiconductor material while using the plurality of gate structures as a first implantation mask, resulting in light dose extension implants in the shared source region and in the shared drain region;

protecting the shared drain region with a first patterned mask that leaves the shared source region substantially exposed;

implanting a relatively high impurity dose into the semiconductor material while using the plurality of gate structures and the first patterned mask together as a second implantation mask, by bombarding the shared source region with ions of an impurity species at a first tilted angle and toward the second gate structure, resulting in a first heavy dose extension implant in the shared source region; and

implanting another relatively high impurity dose into the semiconductor material while using the second implantation mask, by bombarding the shared source region with ions of the impurity species at a second tilted angle and toward the first gate structure, resulting in a second heavy dose extension implant in the shared source region.

13. The method of claim 12 , further comprising the step of forming a halo implant in the semiconductor material while using the second implantation mask, by bombarding the shared source region with ions at a second tilted angle and toward the second gate structure.

14. The method of claim 12 , wherein the step of protecting the shared drain region comprises forming the first patterned mask such that it covers most of the shared drain region and such that it at least partially covers the third gate structure, and wherein the method further comprises:

removing the first patterned mask after implanting the relatively high impurity dose into the semiconductor material;

thereafter, forming a second patterned mask such that it covers at least eighty percent of the shared drain region and such that it at least partially covers the second gate structure; and

thereafter, implanting a relatively high impurity dose into the semiconductor material while using the plurality of gate structures and the second patterned mask together as a third implantation mask, by bombarding the shared source region with ions of the impurity species at a second tilted angle and toward the first gate structure, resulting in a second heavy dose extension implant in the shared source region.

15. The method of claim 14 , wherein:

the step of protecting the shared drain region comprises forming the first patterned mask such that it completely covers the shared drain region and such that it completely covers the third gate structure; and

the step of forming the second patterned mask comprises forming the second patterned mask such that it completely covers the shared drain region and such that it completely covers the second gate structure.

16. The method of claim 14 , further comprising:

forming a first halo implant in the semiconductor material while using the second implantation mask, by bombarding the shared source region with ions at a third tilted angle and toward the second gate structure; and

forming a second halo implant in the semiconductor material while using the third implantation mask, by bombarding the shared source region with ions at a fourth tilted angle and toward the first gate structure.

17. The method of claim 12 , wherein:

the step of implanting the relatively light impurity dose comprises implanting less than half of a total extension implant dose; and

the step of implanting the relatively high impurity dose comprises implanting the remaining amount of the total extension implant dose.