Ultrahigh thermal-stable p-type WSe<inline-formula><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="TIMEQ1"><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:math></inline-formula> transistors with silicon processing-compatible metal-semiconductor contacts

High-performance p-type transistors are a fundamental and arduous challenge for the development of two-dimensional (2D) semiconductors in CMOS integrated circuits. The lack of a p-type modulation strategy that combines high hole transport and excellent stability seriously hinders the development of 2D p-type transistors. Here, we report a spontaneous oxidation intercalation technique for metal/semiconductor contact interfaces, which achieves high hole transport and excellent thermal stability of tungsten diselenide (WSe$_2$) transistor. A tungsten oxide (WO$_x$) buffer layer is constructed between the contact interface of metal and WSe$_2$ by spontaneous oxidation after plasma etching. This metal-WO$_x$-WSe$_2$ contact interface enhances hole transport and significantly reduces the contact resistance by 10$^3$. Furthermore, the WO$_x$ buffer layer with high thermal stability ensures that the WSe$_2$ transistor maintains almost non decaying p-type characteristics even after long-term annealing up to 400$^\circ$C, meeting the thermal budget for back-end-of-line integration. This contact strategy is compatible with silicon-based processes and has been successfully applied to the construction of homogeneous WSe$_2$ CMOS inverters.