A sensor includes a first chip, a dam structure and a cover. The first chip includes a substrate, a sensing area and a low-k material layer. The sensing area is located on the surface of the substrate. The low-k material layer is located in the substrate. The dam structure is located on the first chip. The dam structure covers the edge of the low-k material layer. The cover is located on the dam structure and covers the sensing area. A manufacturing method of a sensor is also provided.