|A micro detector includes a substrate, a fin structure, a floating gate, a sensing gate, a reading gate and an antenna layer. The fin structure is located on the substrate. The floating gate is located on the substrate and is perpendicularly across the fin structure. The sensing gate is located on one side of the fin structure. The reading gate is located on the other side of the fin structure. The antenna layer is located above the sensing gate and is connected to the sensing gate. An induced charge is generated when the antenna layer is bombarded by an outside energy source. The induced charge is stored in the floating gate through a coupling effect. A defect distribution during a wafer manufacturing process can be estimated by calculating the induced charge.