The global radio frequency (RF) semiconductor market size is growing dramatically in recent years, especially with the growing demand for mobile devices, communication networks, automotive applications, etc. Failure analysis (FA) on RF devices is normally more complex than digital devices, especially when it involves soft failure. This paper discusses FA on an RF product soft failure issue by the pulsed currentvoltage (IV) nanoprobing technique. The device suffered from high-frequency failure and exhibited abnormal repetitive softstart signature. Previous publications on pulsed IV nanoprobing applications were mostly related to Front End Of Line (FEOL) issues and simulations. In most of these cases, the electrical abnormality could also be observed with normal DC IV measurement. In this paper, the pulsed IV nanoprobing was performed at the Back End Of Line (BEOL) interconnects to isolate the failure that was otherwise not detected with normal DC nanoprobing or the reported pulse IV measurement. The proposed method successfully isolate, simulate the failure, and helping us to identify the process and design rule weakness.