A microwave monolithic integrated circuit comprises a T-shaped gate electrode including a Schottky gate electrode formed on a first region of a compound semiconductor substrate, a pair of ohmic electrodes making an ohmic contact with a surface of the substrate in the first region at respective sides of the T-shaped gate electrode, a lower capacitor electrode pattern formed on a second region of the compound semiconductor substrate with a composition substantially identical with a low-resistance, top electrode constituting the T-shaped gate electrode on the Schottky gate electrode, a dielectric film formed on the lower electrode pattern, and an upper electrode pattern formed on the dielectric film.