Method for fabricating an interband tunnel junction, comprising the steps: a) providing a substrate, made of crystalline silicon, and having a first surface; b) implanting first dopants, of a first conductivity type, in the substrate through the first surface; step b) being carried out by a plasma immersion ion implantation technique, so as to obtain a first concentration profile (Pi) of the first dopants in the substrate; c) implanting seconds dopants, of a second conductivity type different from the first conductivity type, in the substrate through the first surface; step c) being carried out by a plasma immersion ion implantation technique, so as to obtain a second concentration profile (P 2) of the second dopants in the substrate; d) applying a heat treatment to the substrate, according to thermal budget; the implantations of steps b) and c) and the thermal budget of the heat treatment of step d) being adapted so that the first profile (P 1) is modified and extends over a first thickness (e 1), and so that the second profile (P 2) is modified and extends over a second thickness (e 2) strictly greater than the first thickness (e 1); the thermal budget of the heat treatment of step d) being adapted so that: - the first and second dopants (2, 3) are electrically activated; - the second dopants have a rate of diffusion into the substrate greater than that of the first dopants, until the following are obtained: a first zone of the substrate having a difference in concentration between the first dopants and the second dopants that is greater than or equal to 5×10 19 at.cm -3, a second zone of the substrate having a difference in concentration between the second dopants and the first dopants that is greater than or equal to 5×10 19 at.cm -3. a) providing a substrate, made of crystalline silicon, and having a first surface; b) implanting first dopants, of a first conductivity type, in the substrate through the first surface; step b) being carried out by a plasma immersion ion implantation technique, so as to obtain a first concentration profile (Pi) of the first dopants in the substrate; c) implanting seconds dopants, of a second conductivity type different from the first conductivity type, in the substrate through the first surface; step c) being carried out by a plasma immersion ion implantation technique, so as to obtain a second concentration profile (P 2) of the second dopants in the substrate; d) applying a heat treatment to the substrate, according to thermal budget; the implantations of steps b) and c) and the thermal budget of the heat treatment of step d) being adapted so that the first profile (P 1) is modified and extends over a first thickness (e 1), and so that the second profile (P 2) is modified and extends over a second thickness (e 2) strictly greater than the first thickness (e 1); the thermal budget of the heat treatment of step d) being adapted so that: - the first and second dopants (2, 3) are electrically activated; - the second dopants have a rate of diffusion into the substrate greater than that of the first dopants, until the following are obtained: a first zone of the substrate having a difference in concentration between the first dopants and the second dopants that is greater than or equal to 5×10 19 at.cm -3, a second zone of the substrate having a difference in concentration between the second dopants and the first dopants that is greater than or equal to 5×10 19 at.cm -3. - the first and second dopants (2, 3) are electrically activated; - the second dopants have a rate of diffusion into the substrate greater than that of the first dopants, until the following are obtained: a first zone of the substrate having a difference in concentration between the first dopants and the second dopants that is greater than or equal to 5×10 19 at.cm -3, a second zone of the substrate having a difference in concentration between the second dopants and the first dopants that is greater than or equal to 5×10 19 at.cm -3. a first zone of the substrate having a difference in concentration between the first dopants and the second dopants that is greater than or equal to 5×10 19 at.cm -3, a second zone of the substrate having a difference in concentration between the second dopants and the first dopants that is greater than or equal to 5×10 19 at.cm -3.