An embedded capacitor structure in a circuit board and a method for fabricating the same are proposed. The circuit board is formed with a first circuit layer on at least one surface thereof, wherein the first circuit layer has at least one first electrode plate for the capacitor structure. Then, a dielectric layer is formed on the first circuit layer and made flush with the first circuit layer. The dielectric layer has a relatively low dielectric constant and good fluidity to effectively fill the spaces between patterned traces of the first circuit later. A capacitive material is deposited on the dielectric layer and the first circuit layer. Finally, a second circuit layer is formed on the capacitive material and has at least one second electrode plate corresponding to the first electrode plate, together with the capacitive material disposed in-between, to form the capacitor structure.