This paper reports on the design and optimization of a 2-Axis, single proof mass MEMS capacitive accelerometer, using the Inertial Measurement Unit (IMU) platform of GlobalFoundries. The accelerometer consists of a square proof mass suspended using crab leg springs. As dual axis accelerometers are designed to work in both in-plane directions, they are prone to cross-coupling between in-plane acceleration and Z-Axis acceleration. This is due to the structural design that makes them sensitive to cross-Axis acceleration. Moreover, low stiffness in Z-Axis causes the proof-mass to sag due to gravity. In the present paper, we address the cross-Axis sensitivity issue in the context of a high-sensitivity, differential capacitive accelerometer in a small footprint of 1.5mm x 1.5 mm, with reduced in-plane cross-Axis sensitivity and high frequency separation among the in-plane and Z-Axis modes. Simulation results show a differential capacitive sensitivity of 59fF/g (g=9.8 m/s2) can be achieved. The device also has a mode separation of 10 kHz between in-plane and out-of-The plane modes. The average cross-Axis sensitivity in XY is 1.33% and the cross-Axis sensitivity due to Z-Axis acceleration is zero.