Devices sensitive to all three components of a magnetic-field vector are presented. The sensitivity to two field components in the plane of the chip is achieved by merging two one-dimensional vertical magnetotransistors positioned at a 90 degrees angle to each other. An additional surface-collector pair makes this device also sensitive to the last field component, which is perpendicular to the plane of the chip. The sensitivity of the 3-D sensor is represented by a nondiagonal sensitivity-matrix. The smallest achieved sensitive volume is (6*10*16) mu m/sup 3/, which is limited by the design tolerances. The elements of the sensitivity matrix of the device are discussed along with the parameters that influence them. The influence of additional collector pairs on the sensitivity is also discussed. Several 3-D sensitive structures are presented, including magnetotransistor and resistive structures. >