FIELD OF THE INVENTION

The present invention relates to a capacitor.

BACKGROUND OF THE INVENTION

As a typical capacitor element for use in semiconductor integrated circuits, for example, a MIM (Metal Insulator Metal) capacitor is well known. The MIM capacitor is a capacitor that has a parallel plate-type structure with an insulator sandwiched between a lower electrode and an upper electrode.

For example, Patent Document 1 discloses a technique for providing a thin film MIM capacitor that prevents insulation characteristics and leakage current characteristics from being degraded. The thin film MIM capacitor described in Patent Document 1 has a substrate, a lower electrode made of a noble metal formed on the substrate, a dielectric layer thin film formed on the lower electrode, and an upper electrode made of a noble metal formed on the dielectric thin film. The capacitor also includes an external electrode for electrically connecting the upper electrode and the lower electrode to the outside.

Patent Document 1: Japanese Patent Application Laid-Open No. 2010-109014

SUMMARY OF THE INVENTION

However, when the external electrode extends beyond a region where the upper electrode is formed, the external electrode and the lower electrode may come close to each other, thereby leading to capacitive coupling with a protective layer (also referred to as an interlayer film) interposed therebetween. As a result, parasitic capacitance made by the external electrode, the protective layer, and the lower electrode is generated, which is connected in parallel with the true capacitance made by the upper electrode, the dielectric film, and the lower electrode. In this specification, this parasitic capacitance is referred to as protective layer capacitance.

For example, in a capacitor that requires a Q value in an RF circuit, the presence of protective layer capacitance causes unnecessary parasitic capacitance in the capacitor, which in turn causes the Q value of the capacitor to be decreased. In addition, the protective layer capacitance fluctuates due to changes in properties of the protective layer material at high temperature or high humidity, which then causes the Q value of the capacitor to fluctuate.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a capacitor which has a high Q value even at high temperature or high humidity, with protective layer capacitance reduced.

A capacitor according to an aspect of the present invention includes a substrate, a lower electrode on the substrate, a dielectric film on the lower electrode, an upper electrode on a part of the dielectric film, a protective layer that covers the lower electrode and the upper electrode, and an external electrode that penetrates the protective layer. The external electrode is formed only in a region defined by a periphery of the upper electrode in a plan view of the capacitor viewed from an upper surface thereof towards the substrate.

According to the present invention, a capacitor can be provided which has a high Q value even at high temperature or high humidity, with protective layer capacitance reduced.

