A semiconductor die (100; 200) comprising: - a semiconductor body (2, 6), formed by a substrate and an epitaxial layer provided on the substrate, having a front side and a back side, and housing an electronic circuit in the epitaxial layer; - a buried region in the substrate between the electronic circuit and the back side, including a first layer of conductive material and a dielectric layer extending between the first layer of conductive material and the substrate; - first and second trenches extending at a distance from one another; - a first conductive path extending along a direction within said first and second trenches, through the epitaxial layer and part of the substrate and between the buried region and the front side, forming a first path for electrical access to the first layer of conductive material; wherein said first layer of conductive material forms a first plate of a capacitor buried in the substrate, wherein the buried region further comprises a second layer of conductive material, between the dielectric layer and the substrate, which forms a second plate of said capacitor, the dielectric layer being the dielectric of said capacitor arranged between the first and second plates of said capacitor, the semiconductor die (100; 200) further comprising a second conductive path extending along said direction in said first and second trenches through the epitaxial layer and part of the substrate and between the buried region and the front side, forming a second path for electrical access to the second layer of conductive material, said electronic circuit being arranged in a region of the semiconductor body (2, 6) between the first and the second trench and being superimposed, in a top plan view, to the buried region. - a semiconductor body (2, 6), formed by a substrate and an epitaxial layer provided on the substrate, having a front side and a back side, and housing an electronic circuit in the epitaxial layer; - a buried region in the substrate between the electronic circuit and the back side, including a first layer of conductive material and a dielectric layer extending between the first layer of conductive material and the substrate; - first and second trenches extending at a distance from one another; - a first conductive path extending along a direction within said first and second trenches, through the epitaxial layer and part of the substrate and between the buried region and the front side, forming a first path for electrical access to the first layer of conductive material; wherein said first layer of conductive material forms a first plate of a capacitor buried in the substrate, wherein the buried region further comprises a second layer of conductive material, between the dielectric layer and the substrate, which forms a second plate of said capacitor, the dielectric layer being the dielectric of said capacitor arranged between the first and second plates of said capacitor, the semiconductor die (100; 200) further comprising a second conductive path extending along said direction in said first and second trenches through the epitaxial layer and part of the substrate and between the buried region and the front side, forming a second path for electrical access to the second layer of conductive material, said electronic circuit being arranged in a region of the semiconductor body (2, 6) between the first and the second trench and being superimposed, in a top plan view, to the buried region.