Semiconductor devices and fabrication methods thereof are provided. The semiconductor devices include: a substrate, the substrate including a p-type well adjoining an n-type well; a first p-type region and a first n-type region disposed within the n-type well of the substrate, where the first p-type region at least partially encircles the first n-type region; and a second p-type region and a second n-type region disposed in the p-type well of the substrate, where the second n-type region at least partially encircles the second p-type region. In one embodiment, the first p-type region fully encircles the first n-type region and the second n-type region fully encircles the second p-type region. In another embodiment, the semiconductor device may be a bipolar junction transistor or a rectifier.