Ion implanted silicon planar varactor diodes of large capacitance variation ratio have been developed for UHF/VHF TV tuner circuits. The ratio of the capacitance variation achieved at 3 V to 25 V is between 6 and 7 with devices exhibiting low leakage and a required breakdown voltage of 30 V. Ion implantation has been used to introduce phosphorus into n-type silicon in the predeposition cycle. The device fabrication is completed using conventional diffusion techniques which also include thermal annealing. The fabrication process involves a minimum number of processing steps to produce low-cost devices. These diodes were used in a VHF TV tuner to obtain gain between 18 and 32 db in different bands, indicating high values of the quality factor of the varactors.