According to embodiments, an insulated gate bipolar transistor (IGBT) may include a first conductive type collector ion implantation area, formed within a substrate, second conductive type first buffer layers, formed over the collector ion implantation area and each including a first segment buffer layer and a second segment buffer layer, a first conductive type poly layer formed from a surface of the substrate to the collector ion implantation area, the first conductive type poly layer having a contact structure, a second buffer layer of the second conductive type, formed in the substrate area next to the first conductive type poly layer. According to embodiments, a segment buffer layer may have different concentrations according areas. Accordingly, amounts of hole currents injected through the buffer layers may differ according to areas.