In this paper analytical modeling for a novel three region gate dielectric engineered AlGaN/GaN Metal Insulator Semiconductor heterostructure field effect transistor (MISHFET) device architecture is presented which shows high transconcluctance and enhanced cut-off frequency at quarter micron gate lengths. Using a three region analysis along the horizontal direction in the gate dielectric region the expressions for transconcluctance and cut-off frequency of the device are obtained. It has been observed that using these gate dielectric schemes, improvements on device performance are observed over conventional MISHFET structures. Relative comparison of T and F-gate shaped structures is done with uniform gate dielectric profile and enhancement in microwave performance is observed. The proposed model is capable of modeling electrical characteristics like drain current, output conductance and threshold voltage of various other existent structures like uniform gate dielectric MISHFETs, HFETs and T-gate HFETs. The present model is based on closed form expression and does not involve any fitting parameter. The results obtained are compared with experimental data and show excellent agreement, thereby proving the validity of the model. (C) 2008 Elsevier Ltd. All rights reserved.