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In this letter, we comprehensively investigate the electrical properties of the 1200 V planner-gate 4H-SiC power metal–oxide–semiconductor field-effect transistors under the mechanical strains. Three kinds of strains, including the biaxial strain, uniaxial strain parallel to the gate channel, and uniaxial strain perpendicular to the gate channel, are applied using the wafer bending system. It is found that all kinds of compressive strains improve the drain current (Id) under the same gate voltage (Vg) and shift the threshold voltage (Vth) negatively, while the tensile strains decrease Id and shift Vth positively. The Vth shift mainly results from the strain modulated band structure in the poly-Si gate. Under the same overdrive gate voltage (Vov), biaxial strains merely change Id, while both the parallel and perpendicular uniaxial compressive strains enhance Id. The uniaxial compressive strain elevates the electron mobility in the inverted channel by repopulating more electrons into the valleys with a smaller conduction effective mass, which results in the current improvement. [ABSTRACT FROM AUTHOR]