Asymmetric Source and Drain Structures in Semiconductor Devices

A semiconductor device, comprising:

• a first active area and a second active area on a substrate, wherein the first active area comprises a first source/drain structure formed over a first fin structure, and the second active area comprises a second source/drain structure over a second fin structure;
• a first gate structure and a second gate structure over the first and the second fin structures, respectively, the first and second source/drain structures being proximate the first and second gate structures, respectively;
• a first metal silicide layer on the first source/drain structure in the first active area;
• a second metal silicide layer on the second source/drain structure in the second active area;
• and
• a first and second conductive features on the first and the second metal silicide layers, respectively, wherein the first metal silicide layer has a first contact surface area to the conductive feature greater than a second contact surface area of the second metal silicide layer to the second conductive feature.

A semiconductor device, comprising:

• a first source/drain structure over a first fin structure, a second source/drain structure over a second fin structure, a third source/drain structure over a third fin structure, and a fourth source/drain structure over a fourth fin structure, wherein the first source/drain structure has a first vertical height, the second source/drain structure has a second vertical height, the third source/drain structure has a third vertical height, and the fourth source/drain structure has a fourth vertical height, the first source/drain structure and the third source/drain structure having a first conductivity type, the second source/drain structure and the fourth source/drain structure having a second conductivity type, wherein the third vertical height different from the fourth vertical height, wherein the first vertical height is less than the third vertical height, wherein the second vertical height is less than the third vertical height;
• a first metal silicide layer on the first source/drain structure;
• a second metal silicide layer on the second source/drain structure;
• and
• a first and second conductive features on the first and the second metal silicide layers, respectively;
• wherein the first metal silicide layer has a first contact surface area to the first conductive feature greater than a second contact surface area of the second metal silicide layer to the second conductive feature.