A semiconductor device having a lateral diode includes a semiconductor layer, a first semiconductor region in the semiconductor layer, a contact region having an impurity concentration greater than that of the first semiconductor region, a second semiconductor region located in the semiconductor layer and separated from the contact region, a first electrode electrically connected through the contact region to the first semiconductor region, and a second electrode electrically connected to the second semiconductor region. The second semiconductor region includes a low impurity concentration portion, a high impurity concentration portion, and an extension portion. The second electrode forms an ohmic contact with the high impurity concentration portion. The extension portion has an impurity concentration greater than that of the low impurity concentration portion and extends in a thickness direction of the semiconductor layer.