Plasma Immersion Ion Implantation has several unique advantages over conventional implantation, such as low cost, large area capability, non-line-of-sight features and high dose rate implantation. However, it is still far from use in routine production because of problems such as the ability to control the ion depth profile in targets, the ion dose and contamination. In this thesis, a PIII system has been systematically calibrated, and a computer simulation code for PIII has been developed in order to understand more clearly the physics of the PIII process and to optimise the experimental conditions. In the second part of this thesis, a new application of PIII has been explored, where the PIII technique has been used as a high dose-rate implant treatment to form amorphous silicon nitride/oxide films on both crystalline and amorphous silicon substrates. The electrical properties of these films have been characterized. It shows that low dose nitrogen/oxygen implantation leads to the modification of Schottky barrier heights or the introduction of charged defects in the materials. As the ion dose is increased, alloying effects take over, forming silicon nitride/oxide alloys. The a-SiNx:H films synthesized via PIII have electrical characteristics similar to those grown by PECVD, but a-SiOx:H has different electrical properties from a-SiNx:H.