An under the cabinet microwave should be 16 to 18 inches from the stove top. Placing the microwave any closer to the stove top could cause damage to the bottom of the microwave. If the height of the cabinets does not provide the necessary clearance, the cabinets should be raised.
Mounting a microwave over the range frees up valuable counter space. Most over-the-range microwaves feature a light and ventilation for the stove top below. The bottom surfaces of cabinets are required to be at least 30 inches above the top of the stove.