A semiconductor structure including SRAM cells with improved write margins and a method for forming the same are provided. The semiconductor structure comprises a substrate including a core circuit and an SRAM cell. The SRAM cell includes a pull-up PMOS device that comprises a first source/drain region in the substrate, a first SiGe stressor having a portion overlapping at least a portion of the first source/drain region, and a first current-tuning region having a portion overlapping at least a portion of the first source/drain region. The core circuit comprises a core PMOS device that comprises a second source/drain region in the substrate, and a second SiGe stressor having a portion overlapping at least a portion of the second source/drain region. The core PMOS device is free of current-tuning regions.