A bipolar transistor device includes a substrate and at least one first transistor unit. The first transistor unit includes a first doped well of first conductivity type, at least one first fin-based structure and at least one second fin-based structure. The first fin-based structure includes a first gate strip and first doped fins arranged in the first doped well, and the first gate strip is floating. The second fin-based structure includes a second gate strip and second doped fins arranged in the first doped well, and the second gate strip is floating. The first doped fins, the second doped fins and the first doped well form first BJTs, and the first doped fins and the second doped fins are respectively coupled to high and low voltage terminals.