A novel single-chip microelectromechanical systems (MEMS) capacitive microphone with a slotted diaphragm for sound sensing is developed to minimize the microphone size and improve the sensitivity by decreasing the mechanical stiffness of the diaphragm. According to the results, a clamped microphone with a diaphragm and a slotted one with a diaphragm have the same mechanical sensitivity, but the size of slotted microphone is at least 1.62 times smaller than clamped structure. The results also yield a sensitivity of for the clamped and for the slotted microphone with a diaphragm. The sensitivity of the slotted diaphragm is increased 7.27 times. The calculated pull-in voltage of the clamped microphone is , the measured pull-in voltage of the slotted one is . The pull-in voltage of the slotted microphone is about 50% decreased.