Electronic device including a transistor structure having an active region adjacent to a stressor layer and a process for forming the electronic device
View Patent ↗An electronic device can include a transistor structure of a first conductivity type, a field isolation region, and a layer of a first stress type overlying the field isolation region. For example, the transistor structure may be a p-channel transistor structure and the first stress type may be tensile, or the transistor structure may be an n-channel transistor structure and the first stress type may be compressive. The transistor structure can include a channel region that lies within an active region. An edge of the active region includes the interface between the channel region and the field isolation region. From a top view, the layer can include an edge the lies near the edge of the active region. The positional relationship between the edges can affect carrier mobility within the channel region of the transistor structure.
1. An electronic device comprising:
a first transistor structure of a first conductivity type including a first active region having a first edge and a second edge, wherein:
the first edge has a length that extends substantially along a channel length direction of the first transistor structure; and
the second edge has a length that extends substantially along a channel width direction of the first transistor structure;
a field isolation region adjacent to the first active region; and
a layer of a first stress type larger than the first active region overlying the field isolation region, wherein from a top view:
the layer is not part of a sidewall spacer structure for the first transistor structure;
a first edge of the layer lies adjacent to the first edge of the first active region;
a second edge of the layer lies adjacent to the second edge of the first active region;
a first distance is a distance between the first edge of the first active region and the first edge of the layer;
a second distance is a distance between the second edge of the first active region and the second edge of the layer; and
the first distance is less than the second distance.
2. The electronic device of claim 1 , wherein the first conductivity type is p-type and the first stress type is tensile.
3. The electronic device of claim 1 , wherein the first conductivity type is n-type and the first stress type is compressive.
4. The electronic device of claim 1 , wherein:
the first active region comprises a channel width;
the first active region underlies an opening within the layer, wherein from a top view, the opening has a dimension that is measured in a direction substantially parallel to the channel width; and
the dimension is no greater than approximately a sum of the channel width and one unit of misalignment tolerance for a mask used to define the opening within the layer of the first stress type.
5. The electronic device of claim 1 , further comprising a second transistor structure including a second active region, wherein:
the second transistor structure has a second conductivity type opposite the first conductivity type;
the second active region lies adjacent to the first active region; and
the layer overlies the second active region.
6. The electronic device of claim 5 , wherein:
substantially none of the first active region is covered by the layer; and
substantially all of the second active region is covered by the layer.
7. The electronic device of claim 3 , wherein the first active region comprises a primary surface lying on a (100) or (110) crystal plane and oriented substantially in a direction of form <110>.
8. A process of forming an electronic device comprising:
forming a field isolation region extending into a semiconductor layer, wherein from a top view, after forming the field isolation region, a first active region has a first edge and a second edge and is surrounded by the field isolation region;
forming a transistor structure of a first conductivity type that includes the first active region, wherein:
the first edge of the first active region has a first length that extends substantially parallel to a channel length direction of the transistor structure; and
the second edge of the first active region has a second length that extends substantially parallel to a channel width direction of the transistor structure;
forming a layer of a first stress type larger than the first active region overlying the field isolation region and first active region; and
patterning the layer to define an opening, wherein from a top view:
a first edge of the opening lies adjacent and substantially parallel to the first edge of the first active region;
a second edge of the opening lies adjacent and substantially parallel to the second edge of the first active region;
a first distance is a distance between the first edge of the first active region and the first edge of the opening;
a second distance is a distance between the second edge of the transistor and the second edge of the opening; and
the first distance is not greater than the second distance.
9. The process of claim 8 , wherein the first conductivity type is p-type and the first stress type is tensile.
10. The process of claim 8 , wherein the first conductivity type is n-type and the first stress type is compressive.
11. The process of claim 8 , wherein:
forming the transistor structure comprises forming the transistor structure, such that the first active region comprises a channel width; and
patterning the layer comprises forming the opening, such that, from a top view, the opening has a dimension that is measured in a direction substantially parallel to the channel width, and the dimension is no greater than approximately a sum of the channel width and one unit of misalignment tolerance for a mask used to pattern the layer.
12. The process of claim 10 , wherein forming the field isolation region comprises forming the field isolation region, such that each of the first and second active regions comprises a primary surface lying on a (100) or (110) crystal plane and oriented substantially in direction of form <110>.