A manufacturing method of an electronic device, comprising the steps of: - forming a drift layer having a top surface opposite to a bottom surface, and a first conductivity type; - forming a trench in the drift layer by etching the drift layer starting from the top surface in a region of the drift layer where, in subsequent steps, the active area of the device will be formed; - forming an edge-termination structure laterally to said trench by implanting dopant species which have a second conductivity type different from the first conductivity type; and - forming a depression region between said trench and said edge-termination structure by digging the drift layer starting from the top surface, characterized in that the steps of forming the depression region and the trench are carried out at the same time, in that the step of forming the depression region comprises patterning the drift layer to define opposite side walls, wherein the side wall closer to the edge-termination structure forms a sloped region having a first slope, and in that the step of forming the trench comprises etching the drift layer to define side walls of the trench which have a second slope steeper than the first slope, said depression region extending between the edge-termination structure and the trench, wherein the step of forming at the same time the depression region and the trench comprises the substeps of: forming a first etching mask having a first opening and a second opening; forming a second etching mask in a position corresponding to the second opening of the first etching mask, a first portion of said second etching mask having a thickness that decreases according to the first slope; carrying out an etching step to form the trench and the depression region, whereby the etching step removes surface portions of the second etching mask thereby progressively exposing further portions of the drift layer which are below said first portion, and removes the portions of the drift layer which are exposed through the first opening and the further portions of the drift layer which are exposed following upon progressive removal of the second etching mask. - forming a drift layer having a top surface opposite to a bottom surface, and a first conductivity type; - forming a trench in the drift layer by etching the drift layer starting from the top surface in a region of the drift layer where, in subsequent steps, the active area of the device will be formed; - forming an edge-termination structure laterally to said trench by implanting dopant species which have a second conductivity type different from the first conductivity type; and - forming a depression region between said trench and said edge-termination structure by digging the drift layer starting from the top surface, forming a first etching mask having a first opening and a second opening; forming a second etching mask in a position corresponding to the second opening of the first etching mask, a first portion of said second etching mask having a thickness that decreases according to the first slope; carrying out an etching step to form the trench and the depression region, whereby the etching step removes surface portions of the second etching mask thereby progressively exposing further portions of the drift layer which are below said first portion, and removes the portions of the drift layer which are exposed through the first opening and the further portions of the drift layer which are exposed following upon progressive removal of the second etching mask.