Process of making insulated- gate field-effect transistors

Claim 1

A process for making an insulated-gate field-effect transistor on a first fixed area of a substrate (1) of semiconductor material, having a first type of conductivity, comprising the steps of: - forming a first insulating layer (4) on at least one second fixed area of said substrate (1), completely enclosing said first fixed area, - forming on a first region of said first fixed area a second insulating layer (5), - forming on said second insulating layer a conducting layer (6) and on said conducting layer a third insulating layer (7), the second insulating layer (7) and the conducting layer (6) capable of building up, respectively, a gate dielectric and a gate electrode of the transistor, and - forming insulating walls at least on the uncovered portions of the edges of the conducting layer, - defining in said first fixed area regions not covered by any layer, separated from each other, and capable of producing source and drain regions of the transistor, characterized by - successive operations to form in the area of at least said first fixed area a layer of non-­monocrystalline semiconductor material (18), - introducing through ion implantation at least into a portion of the layer of non-monocrystalline semiconductor material (18) impurities capable of producing in said layer a second type of conductivity opposite to said type of conductivity, and - a thermal oxidizing operation capable of converting at least a portion of the non-monocrys­talline semiconductor material (18) into insulating material, and transferring into the regions (20, 21) capable of forming source and drain regions of the transistor at least a portion of the impurities introduced into the layer of non-monocrystalline semiconductor material (18).