The invention provides two types of
silicon-on-insulator (SOI) structures with step-type
buried oxide layers. The first type of SOI structure comprises a P-type
semiconductor substrate, a gate
insulation layer formed above a P-type channel, a grid
electrode formed above the gate
insulation layer and a side wall which covers the grid
electrode and the side edge of the gate
insulation layer, wherein an N-type source region, an N-type drain region, the step-type
buried oxide layers positioned in the N-type source region and the N-type drain region and below the P-type channel are formed on the
semiconductor substrate; the thicknesses of the
buried oxide layers positioned in the N-type source region and the N-type drain region are respectively greater than that of the buried
oxide layer positioned below the P-type channel; and a P-type element heavily doped region is arranged in the P-type
semiconductor substrate below the corresponding thinner buried
oxide layer below the side wall adjacent to one side of the N-type drain region. Different from the first type of SOI structure, the second type of SOI structure is characterized in that the top of the substrate is provided with the N-type doped region, and the source region and the drain region are P-type. By utilizing the technical scheme of the invention, the
short channel effect of the existing SOI structures can be solved.