**1. Introduction**

The analytical model and simulation numerical of semiconductor devices is one of the important steps for Integrate Circuit fabrication, verication and characterization. Each semiconductor device has models that satises the requirements to the device under different operating conditions. GaAs MESFET is a promising semiconductor device used in many applications in the microwave domain. The elements which compose the MESFET transistors can be gathered in two distinct categories. There are extrinsic and intrinsic elements; the first category represents the different structures of access like the side resistances *Rs* and *Rd*. The intrinsic elements like the transconductance *gm* and drain conductance *gd* translate by their nature and their behavior localized of the device physical structure. Our main aim in these sheets related on the one hand to the optimization of a two dimensional (2D) analytical model for the static characteristics of short gate-length GaAs MESFET's, this model takes into account the different physical specific phenomena of the device, and on the other hand to calculate the variation of some intrinsic elements (transconductance and drain conductance) as a function of the biasing voltages. The model suggested has enables to us to calculate and trace the different series from curves. The results obtained are well represented and interpreted.
