The invention provides an SOI device capable of improving a self-
heating effect and a preparation method thereof. The preparation comprises the steps: providing a
semiconductor substrate with a cavitystructure, enabling the cavity structure to be located in a top
semiconductor layer and exposing an insulating layer, preparing an active region
coating the cavity structure, and preparing a gate
electrode structure, a source-drain region and a source-drain
electrode. The
SOI substrate with the nanoscale cavity is adopted, the cavity structure is located in the top
semiconductor layer, the size of the cavity is effectively reduced, the cavity is in the nanoscale size in the channel length direction, the heat dissipation path of the device cannot be obviously blocked, and compared with a device with a large-size cavity, the self-
heating effect is relieved. Theoretically, the thickness of the top semiconductor layer above the cavity can reach 2 nm, it is guaranteed that top
silicon is not damaged, a channel can be completely exhausted by a gate
electrode, and the
floating body effect is effectively restrained. The cavity is located in the top semiconductor layer and makes contact with the insulating layer, parasitic charges in the insulating layer cannot be introduced into a parasitic channel at the bottom of the top semiconductor layer, and the
total dose radiation effect is effectively restrained.