The growth of undoped, p-type, and n-type silicon nanowires (SiNWs) has been systematically investigated using the low pressure chemical vapor deposition. The effect of the chamber pressure on the growth is observed. The growth windows of SiNWs with different diameters of Au nanoparticles as catalysts were also found. The growth mechanism of Silicon nanowires and native oxide on the SiNWs are analyzed by transmission electron microscope (TEM). The SiNWs FET was fabricated successfully. Single crystal p-type SiNWs have been prepared and characterized by electrical transport measurements.