Electric Vehicles (EVs) play an integral role in electrification of transportation sector from conventional internal combustion engines. Inverters adopted in electric vehicles should meet the competing requirements of low cost, compactness, and less weight. Modern EV inverters employ Silicon Carbide (SiC) based MOSFETs due to their high thermal flux carrying capacity and ability to withstand higher junction temperatures. The junction temperature should not surpass the threshold value; exceeding it would deteriorate its electrical performance and eventually damage the inverter. Thus, the thermal management of the inverters is paramount to ensure safe and reliable operation. Air-cooled heat sinks are widely adopted and studied in the thermal management of electronic devices. The current study conducts three-dimensional steady-state conjugate turbulent heat transfer analysis on air-cooled conventional plate-fin heat sink (PFHS) with two SiC MOSFET devices. Contrary to the studies available in the literature, the present study considers all the composite layers of MOSFET, thereby accurately modeling and predicting the thermal resistances of actual device. Additionally, as the junction is a point source, a uniform heat generation boundary condition is employed instead of the commonly imposed uniform heat flux. The equations governing turbulent fluid flow and heat transfer are solved using a Computational Fluid Dynamics (CFD) solver with SST k-omega turbulence closure. A novel air-cooled plate-fin heat sink is proposed with design modifications to the PFHS. In the PFHS, semi-elliptical grooves are incorporated of equal volume in stream-wise (PFHSSt) and span-wise (PFHSSp) directions and compared their thermal performance with the conventional heat sink. The simulated results indicate that PFHSSp exhibits better heat transfer performance than PFHS and PFHSSt. Further, 33% of the removed volume is incorporated as different columnar pins (cylindrical : PFHSSpC, square : PFHSSpS and 45° square : PFHSSpS-45°) in between the plate fins of PFHSSp. Results indicated that the modified heat transfer coefficient of PFHSSpS-45° is around 46%, 1%, and 5% greater than the PFHS, PFHSSpC, and PFHSSpS respectively. It is also observed that the thermal resistance of PFHSSpS-45° is around 23% and 3% lesser than the PFHS and PFHSSpS respectively.