Here we demonstrate a two-dimensional β-gallium oxide-based high electron mobility transistor (HEMT) comprising of a finite gap—access region gap (L_ARG ) in Ohmic-contact access regions with record transconductance linearity. Apart from limiting two-dimensional electron gas (2DEG) density n_s dependency on gate voltage, higher saturation current is estimated for the proposed design. Since the access regions length directly affects the Capacitance of the device and resultant switching applications. In this work, the effect of the gate-source and gate-drain length on device linearity is performed using Atlas-2D simulations. C-V characteristics of the proposed device are explained based on the physical explanation and validated using appropriate models. The higher values of transconductance g_m and current gain cut-off frequency f_T on a large span of operating voltages ensure improved transistor performance for low-noise amplification and RF application and are reported for the first time.