Various embodiments provide an MOS transistor, a formation method thereof, and an SRAM memory cell circuit. An exemplary MOS transistor can include a semiconductor substrate including a first groove on one side of a gate structure and a second groove on the other side of the gate structure. The first groove can have a sidewall perpendicular to a surface of the semiconductor substrate. The second groove can have a sidewall protruding toward a channel region under the gate structure. A stressing material can be disposed in the first groove to form a drain region and in the second groove to form a source region. Stress generated in the channel region of the MOS transistor can be asymmetric. The MOS transistor can be used as a transfer transistor in an SRAM memory cell circuit to increase both read and write margins of the SRAM memory.