defining and for diffusing through as will be understood by those possessing an ordinary skill in the pertinent arts the oxide must be thin enough to diffuse through but thick enough to prevent the underlying diffused surface from being significantly roughened in the afore incorporated 39 671 patent a layer thickness between 1000 u00e5 2000 u00e5 was used the present invention provides advantages by using a much thinner layer that is nonetheless sufficiently thick to prevent surface roughening thereby allowing for even a higher concentration of p silicon to be formed by increasing the p concentration an even lower temperature dependence of a resulting soi device may be achieved another unanticipated advantage of the present invention is associated with the ability to accurately define even finer feature sizes on the order of less than 1 u03bcm than in the afore incorporated 39 671 patent this enables one to reduce the overall size of the entire device layout while maintaining or even improving the quality of pattern definition this increases yield and thus decreases the cost per chip while enabling one to actually add high precision components i e additional resistors traces contact regions etc within a smaller overall pattern layout the improved definition accuracy also significantly reduces pattern to pattern variation across an entire wafer thus leading to significant improvements in the control of the resultant soi device performance characteristics this in turn makes matching of devices such as sensors which is sometimes required for particular applications much easier another unanticipated advantage is associated with the ability to now use significantly thicker oxide films on.