To provide a light modulator of a low VπL in a state that a characteristic impedance Zc of a traveling wave electrode is maintained at a predetermined value using a lithium niobate film formed on a substrate.SOLUTION: A light modulator includes: a substrate 4; a lithium niobate film 5 having a ridge shape part 6 formed on a main surface of a substrate 4; a buffer layer 7 formed on the ridge shape part 6; first electrodes 2a, 2b formed in contact with an upper surface of the buffer layer 7; a dielectric layer 8 arranged in contact with the upper surface of the buffer layer 7; and at least second electrodes 3a, 3b, and 3c arranged so as to be spaced apart from the first electrodes 2a, 2b. The first electrodes 2a, 2b consist of an upper side portion having a side surface not in contact with a dielectric layer 8 and a lower side portion having the side surface in contact with the dielectric layer 8. At least one portion of the upper surface of the dielectric layer 8 is in contact with the first electrodes 2a, 2b, and a width of the lower side portion of the first electrodes 2a, 2b is narrower than the upper side portion of the first electrodes 2a, 2b.SELECTED DRAWING: Figure 13
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