Scanning probe microscopy and corresponding evaluation methods enabled nanoscale observation of power semiconductor devices regardless of the material and structure types. We acquired cross-sectional images of a power metal-oxide-semiconductor field-effect transistor (MOSFET) with a Si superjunction (SJ) structure using a method integrating atomic force microscopy, Kelvin probe force microscopy, and scanning capacitance force microscopy. We obtained the internal structure, surface potential, and differential capacitance under the operation state by applying a bias voltage to the Si-SJ power MOSFET.