In this paper, the physical structure, application areas, and design details of PIN diodes highlighted from the literature are summarized. Moreover, the YITAL 0.25 mu SiGe HBT process compatible PIN diode to be used in X-Band transmitter/receiver circuits and monolithic microwave integrated circuit applications is designed using TCAD design tools. Additionally, effects of PIN diode geometry to its performance are also addressed. The anode area of the designed PIN is 16 mu m(2) with square geometry. In addition to above studies, it is suggested to use of guard ring, deep trench isolation, and also a boron implantation under the bottom of each deep trench isolation well due to their positive effects on diode isolation parameters. Some important SPICE parameters are also extracted from the designed PIN diode using the completed DC and AC simulations. The related simulation results and calculations are also given in the paper together with discussions and future works.