Abstract For the improvement of structural and electrical characteristics of diamond, phosphorus implantation was done during the growth of diamond films. The diamond films implanted with phosphorus were subsequently grown again by microwave plasma chemical vapor deposition (MPCVD). Fabricated diamond films were structurally and electrically characterized. From the results of field emission scanning electron microscope (FESEM) and atomic force microscope (AFM), the implanted diamond samples showed the smoother surfaces and new smaller grains on diamond grains as a result of subsequent growth after implantation. It is thought that the small grains pile up among large grains and compensate rough surfaces of diamond which are caused by large grain size of diamond. The sizes of small grains can be also related to the dose of implanted phosphorus ions. Improved field emission characteristics were obtained in the case of the higher ion dose. It is considered that these results are due to the increased emission area from small grains, and more defects formed in diamond.