Double layered film consisting of polyimide/polysiloxane and interface with nano domain structure was fabricated through stepwise layer formation and subsequent aging steps. During aging of film, nano phase separation occurred between the top layer polysiloxane and the upper layer of polyimide, which was observed by transmission electron microscope (TEM). A stable and uniform polysiloxane layer was obtained, showing the reproducible pressure-sensitive adhesion (PSA) property with the peel strength of 8-13 g/inch at even $300^{circ}C$. In addition, the resulting polymide/polysiloxane film was thermo-stable up to $435^{circ}C$, providing the promising properties suitable for application in microelectronics processing.