A semiconductor device includes a substrate, an epitaxial layer, a sinker, an active device, a first buried layer, and a second buried layer. The substrate has a first type conductivity. The epitaxial layer has a second type conductivity, and is located on the substrate. The sinker has the second type conductivity, and is located in the epitaxial layer. The sinker extends from the substrate to an upper surface of the epitaxial layer, and partitions a region off from the epitaxial layer. The active device is located within the region. The first buried layer has the first type conductivity, and is located between the region and the substrate. The second buried layer has the second type conductivity, and is located between the first buried layer and the substrate. The second buried layer connects with the sinker. Because of the above-mentioned configuration, latch-up can be prevented.