Effects of inclusion of n-buffer layer adjoining the p(+) substrate in IGBT structure have been analyzed using the bipolar transistor-DMOSFET model of the IGBT and taking into consideration the confinement of depleted base width of pnp transistor within this additional layer. The forward I-V characteristics of representative symmetrical and asymmetrical IGBT cells have been simulated in two dimensions using integrated systems engineering technology computer aided design (ISE-TCAD) software package. Variation of forward voltage drop and collector output resistance of this cell with n-layer concentration has been studied and its latching behaviour has been examined in terms of both the latching current density and voltage. The forward voltage drop, output resistance, turn-off time, latching current density and voltage of the asymmetrical cell increased with n-layer concentration. At higher doping concentrations of this layer, the asymmetrical IGBT cell characteristics have been found to approximately degenerate to that of the DMOSFET cell with the knee point voltage not clearly discernible.