A Ge and Si hybrid material accumulation mode GAA (Gate-All-Around) CMOSFET includes a PMOS region having a first channel, an NMOS region having a second channel and a gate region. The first channel and the second channel have a circular-shaped cross section and are formed of p-type Ge and n-type Si, respectively; the surfaces of the first channel and the second channel are substantially surrounded by the gate region; a buried oxide layer is disposed between the PMOS region and the NMOS region and between the PMOS or NMOS region and the Si substrate to isolate them from one another. In an accumulation mode, current flows through the overall cylindrical channel, so as to achieve high carrier mobility, reduce low-frequency noises, prevent polysilicon gate depletion and short channel effects and increase the threshold voltage of the device.