A semiconductor device and a cascode circuit are disclosed herein. The semiconductor device includes a first transistor and a second transistor. The first transistor includes a first electrode, a second electrode, a control electrode, and a control pad. The second transistor includes a first electrode, a second electrode, a control electrode, and a control pad. The second electrode of the first transistor is configured to receive a first predetermined voltage. The control electrode of the first transistor is configured to receive an input signal. The first electrode of the second transistor configured to receive a second predetermined voltage. The second electrode of the second transistor is electrically coupled to the first electrode of the first transistor. The control pad is disposed between the first electrode of the second transistor and the control electrode of the second transistor, and is configured to receive a first adjust signal.