Method of manufacturing a semiconductor substrate having dielectric regions

A method of manufacturing a semiconductor substrate having dielectric isolation regions comprising steps of forming an amorphous silicon layer on the surface of a monocrystalline silicon substrate by implanting ions in the surface of said monocrystalline substrate to produce a first layer of amorphous silicon on said substrate, chemically vapor depositing a second amorphous layer of silicon onto said first layer, annealing a selected zone of said amorphous silicon layers to form a crystallized region intended as an active region, subjecting the resulting structure to a thermal oxidation process to form said dielectric isolation regions, and removing an oxide coating formed on the surface of said crystallized region.