NEGF methodology has been used to study the electrostatics of the channel of a nanowire FET. The device is a coaxially gated nanowire FET. This work presents a good understanding of the physics of these devices and the choices of the correct dielectric materials. The change in the saturation current is corroborated with the change in the channel potential profile. Lower value of dielectric constant for the oxide layer significantly changes the potential profile inside the channel.