Coatings produced by HVOF process with very fine powders, -10 microns for example, show very unique and excellent characteristics, quite defferent from those by any conventional spray process. The coatings allow no water pentration at very thin thickness, less than 0.1 mm. Copper coatings keep high electrical conductivity, possible to replace electrical leads. Alumina coatings with 3-5 microns powders keep mostly alpha phase and show high electrical resistivity at very high voltage, close to that of bulk alumina. No HVOF spray systems, however, can produce coatings with very fine powders for actual application due to hardware trobles, such as spitting, nozzle clogging or powder port melt down. Above all, feeding of very fine powders, finer than 10 microns, is almost impossible with any conventional powder feeders, especially at high feed rate and high consistency required for actual production. Our paper will report how we developed an HVOF system which can produce coatings with very fine powders at high production rate without any running trobles, especially a spray gun, free from trobles which most of conventional HVOF spray guns cannot avoid and a powder feeder which can feed any kind of powder, coarse or very fine, at high and accurate production rate. The paper will also report typical coating properties suggesting many new applications in various fields, for example, in semiconductor manufacturing industry.