RELATED APPLICATIONS

This application claims priority to Japanese Patent Application Nos. 2019-064312, filed on Mar. 28, 2019 and 2019-177122, filed on Sep. 27, 2019, the entire content of which is incorporated herein by reference.

BACKGROUND OF TIlE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device.

2. Description of the Related Art

There has been known a semiconductor device using a I-fall element, for example, as a magnetic sensor. The Hall elements have been used in various applications as magnetic sensors capable of detecting a position or an angle in a non-contact manner. The Hall elements include a vertical Hall element and a horizontal Hall element. Of those, the horizontal Hall element is a magnetic sensor which detects a magnetic field component perpendicular to an element surface, while the vertical Hall element is a magnetic sensor which detects a magnetic field component parallel to the element surface. Further, there has been proposed a magnetic sensor in which the horizontal Hall element and the vertical Hall element are combined to two-dimensionally or three-dimensionally detect a magnetic field.

The above-mentioned vertical Hall element is, however, affected more easily by manufacturing variation than the horizontal Hall element, and is more liable to exhibit large variation in sensitivity and offset voltage characteristic than the horizontal Hall element.

The following method has been proposed to calibrate such characteristic variation. In the method an excitation wiring is disposed near the vertical Hall element, and a magnetic field of a predetermined intensity (hereinafter referred to as “calibration magnetic field”) is generated by the constant current flowing through the excitation wiring so as to apply to a magnetosensitive portion of the vertical Hall element, and estimate the sensitivity of the magnetosensitive portion (see, for example, U.S. Pat. No. 9,116,192). Specifically, the invention described in U.S. Pat. No. 9,116,192 is directed to the estimation of an actual sensitivity of the magnetosensitive portion by changing the intensity of the calibration magnetic field and measuring a change in Hall voltage generated from the vertical Hall element.

Further, according to the invention described in U.S. Pat. No. 9,116,192, the center position of the excitation wiring is laterally offset from the center position of the magnetosensitive portion in the vertical Hall element, that is, the center position of the excitation wiring and the center position of the magnetosensitive portion are laterally spaced apart from each other.

This arrangement reduces variation in intensity of the calibration magnetic field generated by the excitation wiring due to variation in, for example, the width of the excitation wiring caused by process fluctuation in manufacturing a semiconductor device.

However, in the invention described in U.S. Pat. No. 9,116,192, the excitation wiring and the magnetosensitive portion are laterally spaced apart from each other. That is, since an intensity of a calibration magnetic field generated by the current flowing through the excitation wiring is inversely proportional to a distance from the excitation wiring, the longer the distance between the magnetosensitive portion and the excitation wiring becomes, the lower the intensity of the calibration magnetic field applied to the magnetosensitive portion becomes.

As the intensity of the calibration magnetic field applied to the magnetosensitive portion becomes lower, a change in Hall voltage generated from the vertical Hall element becomes smaller. Thus, with the invention described in U.S. Pat. No. 9,116,192, even though the variation in intensity of the calibration magnetic field to be applied to the magnetosensitive portion can be reduced, accuracy of estimating the actual sensitivity of the magnetosensitive portion lowers since the intensity of the calibration magnetic field is low.

The amount of current flowing through the excitation wiring can be increased, to thereby increase the intensity of the calibration magnetic field applied to the magnetosensitive portion. However, as the amount of current flowing through the excitation wiring becomes larger, the amount of heat generated by the excitation wiring becomes larger.

Further, with the invention described in U.S. Pat. No. 9,116,192, since the center position of the excitation wiring is laterally offset from the center position of the magnetosensitive portion by a large amount, peripheral circuits disposed around the magnetosensitive portion are close to the excitation wiring. In this case, the peripheral circuits are affected by the heat from the closely located excitation wiring. Specifically, since the heat generation in the excitation wiring causes asymmetric temperature distribution in each peripheral circuit, characteristics of each peripheral circuit fluctuate. Accordingly, the increase in amount of current caused to flow through the excitation wiring similarly leads to the lowered accuracy of estimating the actual sensitivity of the magnetosensitive portion.

By increasing a distance between the excitation wiring and each peripheral circuit, the fluctuation of characteristics of each peripheral circuit can be suppressed. However, this is not a practical solution because an increase in an area required for the semiconductor device leads to an increase in cost.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a semiconductor device capable of increasing an intensity of a calibration magnetic field applied to a magnetosensitive portion, and capable of suppressing variation in the intensity.

In order to achieve the above-mentioned object, a semiconductor device according to at least one embodiment of the present invention includes a semiconductor substrate; a vertical Hall element formed in the semiconductor substrate, and having a magnetosensitive portion; a first excitation wiring disposed above the magnetosensitive portion, and configured to apply a first magnetic field to the magnetosensitive portion; and second excitation wirings disposed above the magnetosensitive portion, and side by side on one side and another side of the first excitation wiring, respectively, as viewed in plan view from immediately above a front surface of the semiconductor substrate, and configured to apply second magnetic fields to the magnetosensitive portion.

According to the semiconductor device of the present invention, through superimposing the first magnetic field and the second magnetic fields, the intensity of the calibration magnetic field applied to the magnetosensitive portion can be increased, and the calibration magnetic field adjusted to have a more uniform intensity can be applied to the magnetosensitive portion. As a result, it is possible to increase the intensity of the calibration magnetic field applied to the magnetosensitive portion, and to suppress variation in the intensity.

