MEMS technology is proven to be an enabling technology to realize many components for optical networking applications. Due to its widespread applications, VOA has been one of the most attractive MEMS based key devices in optical communication market. Micromachined shutters and refractive mirrors on top of silicon substrate or on the device layer of SOI (Silicon-on-insulator) substrate are the approaches trapped tremendous research activities, because such approaches enable easier alignment and assembly works. These groups of devices are known as the planar VOAs, or two-dimensional (2-D) VOAs. In this review article, we conduct the comprehensively literature survey with respect to MEMS based planar VOA devices. Apparently MEMS VOA technology is still evolving into a mature technology. MEMS VOA technology is not only the cornerstone to support the future optical communication technology, but the best example for understanding the evolution of optical MEMS technology.