A semiconductor structure includes: a first device; a second device contacted with the first device, wherein a chamber is formed between the first device and the second device; a first hole disposed in the second device and defined between a first end with a first circumference and a second end with a second circumference; a second hole disposed in the second device and aligned to the first hole; and a sealing object for sealing the second hole. The first end links with the chamber, and the first circumference is different from the second circumference, the second hole is defined between the second end and a third end with a third circumference, and the second circumference and the third circumference are smaller than the first circumference.