NOVELTY - First electrode layer (70) comprising materials e.g. barium oxide (BaO), strontium oxide (SrO), calcium oxide (CaO), scandium oxide (Sc2O3), other oxides and/or mixture of BaSrCaO, Sc2O3 and metal, is deposited followed by deposition of dielectric oxide spacer layer (80) and second electrode layer (90). Matter from layer (80), is removed and microminiature thermionic converter (MTC) is manufactured.    USE - For use in satellite and deep space missions. Also used in new smaller gas fired combined-cycle plants, with solar concentrators or central receiver power towers to generate electricity as stand alone units or in conjunction with other conversion technologies, with home heating systems (furnace and water heaters) and small businesses to feed electricity back into the home/business or its community electric grid.    ADVANTAGE - Close-space thermionic converter demonstrating relatively large current density and relatively high conversion efficiency is obtained. The converters can be retrofitted into almost any system requiring energy conversion from heat to electricity. At lower power space (less than 125 kWe) MTCs are more economical than conventional co-generation systems using machinery with moving components. The spacing element is designed and configured to minimize thermal loses.    DETAILED DESCRIPTION - A first electrode layer comprising materials such as barium oxide (BaO), strontium oxide (SrO), calcium oxide (CaO), scandium oxide (Sc2O3), other oxides and a mixture of BaSrCaO, Sc2O3 and/or metal, is deposited followed by deposition of dielectric oxide spacer layer and a second electrode layer comprising material having composition similar to first electrode layer. Subsequently matter is removed from the dielectric spacer layer to form an interelectrode gap (100). The materials of the electrode layers have different work functions. The spacer layer comprises silica and/or silicon nitride (Si3N4). The MTC is manufactured by depositing a first substrate comprising a dielectric followed by deposition of a second substrate comprising dielectric and semiconductor material. A recess comprising at least one wall and a floor boundary, is formed in the second substrate after which a first conductor having flat surface is formed in the first substrate. A second conductor having flat surface is deposited in the second substrate such that the flat surface extends through the floor boundary and into the recess. The flat surface is then coated with a first coating material and the second flat surface is coated with a second coating material different from the first coating material. The first and second substrates are assembled together so that the flat surfaces are parallel and opposite to each other, with a spacer provided in-between.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic arrangement of a fabricated microminiature thermionic converter.    First electrode layer (70)    Spacer layer (80)    Second electrode layer (90)    Interelectrode gap (100)