Fully differential -axis acceleration sensing often requires complicated multiwafer bonding processes. We present an integrated fully differential complementary metal-oxide semiconductor–micro-electromechanical systems (CMOS-MEMS) -axis accelerometer utilizing planar comb fingers and a pair of single-crystal silicon (SCS) torsional springs. The sidewall capacitors formed by multiple CMOS interconnect metal layers are exploited for fully differential displacement sensing with a common-centroid wiring configuration. Single crystal silicon is used throughout the device to form robust microstructures. A deep reactive ion etching (DRIE)–based microfabrication process with large processing tolerance has been developed to allow monolithic integration of CMOS circuitry with sensor structures and high fabrication yield. With an on-chip low-power, low-noise, dual-chopper amplifier that has a measured gain and power consumption, the fabricated integrated -axis accelerometer demonstrates a sensitivity of and an overall noise floor of .