Integrated resistive element, phase-change memory element including said resistive element, and method of manufacture thereof

A vertical-current-flow resistive element (12) comprising a monolithic region (12) having a first portion (12a) and a second portion (12b) arranged on top of one another and formed by a single material. The first portion has a first resistivity, and the second portion (12b) has a second resistivity, lower than the first resistivity. To this aim, a monolithic region with a uniform resistivity and a height greater than at least one of the other dimensions is first formed; then the resistivity of the first portion (12a) is increased by introducing, from the top, species that form a prevalently covalent bond with the conductive material of the monolithic region, so that the concentration of said species becomes higher in the first portion (12a) than in the second portion (12b). Preferably, the conductive material is a binary or ternary alloy, chosen from among TiAl, TiSi2, Ta, WSi, and the increase in resistivity is obtained by nitridation.