particularly useful for devices requiring closely spaced high conductivity diffused regions fig5 7 illustrate process steps in accordance with an alternate embodiment of the invention in this embodiment a pattern of diffused regions is achieved by prepatterning the spin on dopant layer so that a patterned diffusion mask is not required as illustrated in fig5 a layer 16 of spin on dopant material is applied directly to the surface of a semiconductor substrate 10 other areas of the substrate may of course be covered by oxides nitrides or the like but in the area of interest no diffusion mask is required as above the dopant material is applied by dropping the liquid dopant material onto a substrate and then spinning the substrate at a prescribed rotational speed the spin on doped layer is patterned photolithographically to leave the dopant material in those areas which are to receive a diffusion the dopant material is prebaked as above either before or after the patterning after patterning the spin on dopant material is exposed to a plasma pretreatment as above optionally a capping layer 20 of oxide nitride or the like can be deposited over the pattern of spin on dopant regions the capping layer prevents the out diffusion of dopant from the dopant regions and prevents the unwanted diffusion of dopant material into.