A fin-type field-effect transistor device includes a substrate, insulators, gate stacks and dielectric strips. The substrate includes a first doped region, a second doped region, third doped blocks located above the first doped region and fourth doped blocks located above the second doped region, and fins located above the third doped blocks and the fourth doped blocks, wherein doping concentrations of the third doped blocks are lower than a doping concentration of the first doped region, and doping concentrations of the fourth doped blocks are lower than a doping concentration of the second doped region. The insulators are disposed on the third doped blocks and the fourth doped blocks of the substrate and covering the fins. The dielectric strips are disposed in between the fins, and in between the third doped blocks and the fourth doped blocks. The gate stacks are disposed over the fins and above the insulators.