Transistor device and semiconductor layout structure including asymmetrical channel region

1. A transistor device comprising:

an active region disposed in a substrate, the active region comprising a first region comprising a first length, a second region comprising a second length, and a third region between the first region and the second region, wherein the first length is greater than the second length;

a gate structure disposed over the active region, the gate structure comprising:

a first portion extending in a first direction and disposed over at least the third region of the active region; and

a second portion extending in a second direction perpendicular to the first direction and disposed over at least a portion of the third region and a portion of the second region; and

a source/drain region disposed at two opposite sides of the gate structure;

wherein the first region comprises a first boundary and a second boundary, wherein the first boundary and the second boundary extend in the second direction, the second region comprises a third boundary and a fourth boundary, wherein the third boundary and the fourth boundary extend in the second direction, and the third region comprises a fifth boundary and a sixth boundary, wherein the fifth boundary extends in the second direction;

wherein the first boundary of the first region, the third boundary of the second region, and the fifth boundary of the third region are collinear with each other;

wherein the sixth boundary of the third region is in contact with the second boundary of the first region at a first point and the fourth boundary of the second region at a second point, the sixth boundary of the third region is a slanted line connecting the first point and the second point;

wherein the gate structure is absent from disposing over the first region of the active region;

wherein the gate structure is absent from disposing over at least one area of the second region of the active region.

2. The transistor of claim 1 , wherein the first length of the first region is defined by a distance between the first boundary and the second boundary, and the second length of the second region is defined by a distance between the third boundary and the fourth boundary.

3. The transistor device of claim 1 , wherein the fifth boundary of the third region is in contact with the first boundary of the first region and the third boundary of the second region.

4. The transistor device of claim 3 , wherein the sixth boundary of the third region extends in a third direction between the first direction and the second direction.

5. The transistor device of claim 3 , wherein a distance between a point on the fifth boundary of the third region and a point on the sixth boundary of the third region defines a third length equal to the first length of the first region, and a distance between another point on the fifth boundary of the third region and another point on the sixth boundary of the third region defines a fourth length equal to the second length of the second region.

6. The transistor of claim 1 , wherein the first portion of the gate structure overlaps the sixth boundary of the third region.

7. The transistor device of claim 1 , wherein the second portion of the gate structure overlaps the sixth boundary of the third region.

8. The transistor device of claim 1 , wherein the first portion of the gate structure further overlaps a portion of the second region of the active region.

9. The transistor device of claim 1 , wherein the gate structure further comprises a third portion, and the second portion and the third portion are disposed at two opposite ends of the first portion and are both physically in contact with the first portion.

10. The transistor device of claim 8 , wherein the third portion of the gate structure overlaps the third region and a portion of the second region.

11. The transistor device of claim 1 , wherein the source region is disposed in the first region, and the drain region is disposed in the second region.