Semiconductor device, matching circuit, and filter circuit

A capacitor (1), which is an embodiment of a semiconductor device, is provided with a substrate (10), a first electrode layer (22) provided on the substrate (10), a dielectric film (23) provided on the first electrode layer (22), a second electrode layer (24) provided on the dielectric film (23), a protective layer (26) covering the first electrode layer (22) and the second electrode layer (24), and an external electrode (27) penetrating the protective layer (26). The dielectric film (23) is composed of a silicon oxide, and the ratio of the three-membered ring structure to the four-membered ring structure of the silicon oxide contained in the dielectric film (23) is 0.46 or less. 作为半导体装置的一个实施方式的电容器(1)具备：基板(10)、设置于基板(10)上的第一电极层(22)、设置于第一电极层(22)上的电介质膜(23)、设置于电介质膜(23)上的第二电极层(24)、覆盖第一电极层(22)以及第二电极层(24)的保护层(26)以及贯通保护层(26)的外部电极(27)，电介质膜(23)由硅氧化物构成，电介质膜(23)所含有的硅氧化物的三元环结构与四元环结构的比率为0.46以下。