The semiconductor device is intended for connection with an in-cell type display touch panel having a plurality of common electrodes, a reference voltage for display is applied to the common electrodes in a display drive period, and the common electrodes serve as sensor electrodes in a touch detection period. The semiconductor device includes a DC level shift circuit operable to shift the DC level of a toggle signal output by a toggle drive circuit to the reference voltage. The semiconductor device supplies the reference voltage to the common electrodes of the display touch panel in the display drive period, and performs a guarding action in which at least a part of the plurality of common electrodes is supplied with a toggle signal shifted in DC level in the touch detection period.