A physical quantity sensor includes: a sensor substrate including a first support substrate, a first insulation film and a first semiconductor layer, which are stacked in this order; a cap substrate including a second support substrate disposed on the first semiconductor layer, and has a P conductive type; and multiple electrodes, which are separated from each other. The first support substrate, the first insulation film and the first semiconductor layer have the P conductive type. The physical quantity is detected based on a capacitance between the plurality of electrodes, and the electrodes are disposed in the first semiconductor layer.