PURPOSE: To make a very sensitive and microminiaturized and highly integrated element by insulating a first and a second active layer with a semi-insulating gallium arsenide layer.

CONSTITUTION: On the surface of a substrate, a first active layer 2 which is an n-type gallium arsenide layer, a semi-insulating gallium arsenide layer 3, and a second active layer 4 which is an n-type gallium arsenide layer are deposited in this order. On both ends of the first active layer 2 and the second active layer 4, a first electrode pair 5, 6a and a second electrode pair 7, 6b are located. At right angles with the first and the second electrode pair, a third electrode pair 8, 9 and a fourth electrode pair 10, 11 are located. Due to this structure, current flows in the second active layer reversely to in the first active layer. When taking out Hall voltage, one end of the third and the fourth electrode pair is set at the same potential and then Hall voltage is taken out at the other end. By this method, the series combination of electromotive forces of the two layers can be obtained.