This letter presents a continuously tunable resonator with a novel triangular doped area on a silicon substrate. The resonator and its tunable element (an n + pp + junction) are co-designed in the same flow, leading to new tradeoffs and novel behaviors. The co-design flexibility allows the active area to be drawn with any doping shape. The base of the triangular doped area is located at the end of a stub. Consequently, when the junction is forward biased with a low bias voltage, the resonator is ended by a short circuit at the triangle base. Then, by increasing the voltage, the short-circuit plan moves continuously until it reaches the top of the triangle, thereby decreasing the length of the short-circuited stub. Besides, a demonstrator validates the concept and offers a continuous resonant frequency tunability of 50%, from 2.2 to 3.3 GHz, with a bias voltage from 0 to −1.3 V.