A process for manufacturing an integrated device comprising at least one MOS transistor integrated on a die of semiconductor material of a first type of conductivity having a main surface, wherein the process comprises: forming one or more gate trenches extending from the main surface into the die, coating the gate trenches with an electrically insulating material to obtain corresponding coated lower portions of the gate trenches being coated with corresponding separation insulating layers and corresponding coated upper portions of the gate trenches being coated with corresponding gate insulating layers, filling the coated lower portions of the gate trenches with electrically conductive material forming corresponding field plates, covering the field plates with corresponding splitting insulating layers of electrically insulating material, implanting dopants of a second type of conductivity into the die from the main surface along one or more implantation directions being tilted with respect to the front surface, the dopants being implanted selectively by passing in an implantation zone at the front surface and a lateral surface of the upper portions of the gate trenches and being blocked in a blocking zone at the splitting insulating layers, diffusing the dopants being implanted to form a body region, and filling the coated upper portions of the gate trenches with electrically conductive material forming corresponding gate regions thereby being substantially self-aligned in depth from the main surface with the body region, wherein the process comprises: implanting the dopants selectively by passing through a passing insulating layer (145,335) of electrically insulating material at the passing zone and being blocked by a blocking insulating layer (165,335) of electrically insulating material at the blocking zone having a thickness being lower and higher, respectively, than an implantation threshold, and wherein the process comprises: forming an auxiliary insulating layer of electrically insulating material on the implantation zone over the gate insulating layers and on the blocking zone over the splitting insulating layers to obtain the passing insulating layer (145,335) and the blocking insulating layer (165,335), respectively, and removing the auxiliary insulating layer after said implanting the dopants. forming one or more gate trenches extending from the main surface into the die, coating the gate trenches with an electrically insulating material to obtain corresponding coated lower portions of the gate trenches being coated with corresponding separation insulating layers and corresponding coated upper portions of the gate trenches being coated with corresponding gate insulating layers, filling the coated lower portions of the gate trenches with electrically conductive material forming corresponding field plates, covering the field plates with corresponding splitting insulating layers of electrically insulating material, implanting dopants of a second type of conductivity into the die from the main surface along one or more implantation directions being tilted with respect to the front surface, the dopants being implanted selectively by passing in an implantation zone at the front surface and a lateral surface of the upper portions of the gate trenches and being blocked in a blocking zone at the splitting insulating layers, diffusing the dopants being implanted to form a body region, and filling the coated upper portions of the gate trenches with electrically conductive material forming corresponding gate regions thereby being substantially self-aligned in depth from the main surface with the body region, wherein the process comprises: implanting the dopants selectively by passing through a passing insulating layer (145,335) of electrically insulating material at the passing zone and being blocked by a blocking insulating layer (165,335) of electrically insulating material at the blocking zone having a thickness being lower and higher, respectively, than an implantation threshold, and wherein the process comprises: forming an auxiliary insulating layer of electrically insulating material on the implantation zone over the gate insulating layers and on the blocking zone over the splitting insulating layers to obtain the passing insulating layer (145,335) and the blocking insulating layer (165,335), respectively, and removing the auxiliary insulating layer after said implanting the dopants. implanting the dopants selectively by passing through a passing insulating layer (145,335) of electrically insulating material at the passing zone and being blocked by a blocking insulating layer (165,335) of electrically insulating material at the blocking zone having a thickness being lower and higher, respectively, than an implantation threshold, and wherein the process comprises: forming an auxiliary insulating layer of electrically insulating material on the implantation zone over the gate insulating layers and on the blocking zone over the splitting insulating layers to obtain the passing insulating layer (145,335) and the blocking insulating layer (165,335), respectively, and removing the auxiliary insulating layer after said implanting the dopants. forming an auxiliary insulating layer of electrically insulating material on the implantation zone over the gate insulating layers and on the blocking zone over the splitting insulating layers to obtain the passing insulating layer (145,335) and the blocking insulating layer (165,335), respectively, and removing the auxiliary insulating layer after said implanting the dopants.