Abstract: A semiconductor device includes a gate structure on a substrate, a first spacer on a sidewall of the gate structure, a second spacer on a sidewall of the first spacer, a third spacer on a sidewall of the second spacer, and first and second stacks of an epitaxial layer and a cap layer respectively disposed at first and second sides of the gate structure. Preferably, a part of the second spacer comprises an I-shape, the cap layer includes a planar top surface and an inclined sidewall, the cap layer contacts the second spacer and the third spacer directly, and the cap layer includes a vertical sidewall connected to the inclined sidewall.

Abstract: A method for testing air tightness includes connecting a testing chamber and a storage chamber, supplying negative pressure to the storage chamber, measuring the pressure in the storage or testing chamber to obtain a first pressure value, determining air tightness of the testing chamber according to the negative pressure and the first pressure value, stopping the negative pressure to the storage chamber, measuring the pressure in the storage chamber to obtain a second pressure value, measuring the pressure in the storage chamber after stopping the negative pressure to the storage chamber to obtain a third pressure value, and determining air tightness of the testing chamber according to the second and third pressure values. The device includes testing and storage chambers, a negative pressure generator, and a pressure gauge connected to the storage chamber, which is connected to the testing chamber. The negative pressure generator is connected to the storage chamber.

Abstract: A method for testing air tightness includes connecting a testing chamber and a storage chamber, supplying negative pressure to the storage chamber, measuring the pressure in the storage or testing chamber to obtain a first pressure value, determining air tightness of the testing chamber according to the negative pressure and the first pressure value, stopping the negative pressure to the storage chamber, measuring the pressure in the storage chamber to obtain a second pressure value, measuring the pressure in the storage chamber after stopping the negative pressure to the storage chamber to obtain a third pressure value, and determining air tightness of the testing chamber according to the second and third pressure values. The device includes testing and storage chambers, a negative pressure generator, and a pressure gauge connected to the storage chamber, which is connected to the testing chamber. The negative pressure generator is connected to the storage chamber.