Semiconductor devices are generallly small in size and delicate in circuit design.  Parylene molecules are very active with good penetration capability during its coating process.  It may enter in small crevice with opening of 1 µm and forms a smooth, pinhole-free film on the surface of crevice wall.  Parylene has pretty good dielectric properties and is able to provide excellent protection for semiconductor devices against voltage spikes ( also known as surges) during services, in general, 5 µm-thick Parylene film withstands dc breakdown voltage of  1,000V and above. 

It was found that Parylene is an ideal protection material for micro-electromechanical systems (MEMS) for its resistance to moisture, corrosion, chemical solvents, saline environment as well as good dielectric properties.