The invention provides a finned-type field effect transistor structure and a fabrication method thereof. The finned-type field effect transistor structure comprises a silicon substrate, a finned structure, a gate insulation layer and a gate electrode, wherein the fined structure is arranged on the silicon structure, the gate insulation layer and the gate electrode are arranged on the finned structure, a dual-layer structure is arranged at the middle part of the finned structure below the gate electrode and forms a dual-layer channel structure, an upper channel is arranged at the upper layer of the dual-layer structure, a low channel is arranged at the lower layer of the dual-layer structure, single-layer structures are arranged at the two ends of the finned structure, insulation mediums are arranged between the single-layer structures and the silicon substrate, and the single-layer structures form source-drain extension regions. By isolating the source-drain extension regions from the silicon substrate through the insulation mediums, leakage passages between a source and a drain of the device and between devices are effectively blocked, the leakage current is reduced, and the latch-up effect is effectively avoided; on the other hand, the upper channel and the substrate are connected by a semiconductor material of the lower channel, the cooling performance is high, and the self heating effect is prevented; and moreover, the method provided by the invention is low in cost, and the process is simple and controllable.