The scaling up of wireless operating microelectronics for upcoming Internet of Things (IoT) applications demands high-performance micro-supercapacitors (MSCs) with corresponding high-energy and power capabilities. Indeed, this necessitates the quest for MSC's electrode materials capable of delivering high energy density at high charge/discharge rates. Many multicationic oxides, such as spinel manganese-iron compounds, demonstrate good pseudocapacitive properties as positive electrodes in conventional supercapacitors. However, fulfilling the required fabrication techniques is a challenge for their applications in MSCs. Hence, this study, for the first time, demonstrates the successful deposition of spinel Mn-Fe thin films on a functional platinum-based current collector. The deposition is achieved in a reactive oxygen environment via reactive DC magnetron sputtering techniques and subsequently annealed ex-situ at 600°C in a nitrogen environment. The electrochemical signature in neutral 1 M Na2SO4 aqueous electrolyte is comparable to those reported for spinel type Mn-Fe bulk counterparts. The areal capacitance at 10.0 mV.s-1 is 15.5 mF.cm-2 for 1 µm thick film, exhibiting excellent coulombic efficiency (close to 100%) and long-term cycle stability after 10,000 cycles. Thus, the synthesis of the multicationic pseudocapacitive oxides via compatible microelectronic deposition methods has set a prospective path to achieve very high-performance MSCs for future IoT applications.