This paper investigates the properties of sub-THz compact tunable push-push oscillator in 45 nm FinFET technology. The push-push oscillator is designed to operate at 250 GHz in a modified cross-coupled LC topology. Commanding the FinFET gates separately in independent-mode bestows the push-push oscillator with a simple and efficient means for ~5 GHz tunable performance without external varactors. Moreover, due to the increased transconductance, the stability criteria of oscillation is much relaxed in FinFET based design compared to that of an identical design in single gate MOSFET. No external capacitors are used to realize the LC tank unlike in conventional LC oscillator design. The higher gate-source capacitance of the FinFET is conveniently utilized to substitute for the external capacitor thus reducing parasitics and raising the resonant frequency. The phase noise of the oscillator varies from -82 to -76 dBc/Hz at 1 MHz offset between 0 V and 1 V back gate bias. The compact and tunable characteristics of the proposed sub-THz oscillator, make it ideally suitable for applications such as on-chip wireless interconnects required for kilo-core computing that have hard limits on area and power but requires precision tuning and high bandwidth for extremely fast data rates.