Semiconductor device having a high resistivity layer in direct contact with a polycrystalline silicon layer of high impurity concentration

Claim 1

In a semiconductor device having a first MOS transistor and a second MOS transistor separated by a field oxide layer from the first MOS transistor, a structure comprising: a semiconductor substrate of one conductivity type; a high impurity concentration diffusion region formed in the surface of said semiconductor substrate and doped with an impurity of the opposite conductivity type to that of said substrate, said region being the drain diffusion region of said first MOS transistor; a first polycrystalline silicon layer doped with an impurity of said opposite conductivity type and extending over said field oxide layer, and one end of which is connected with a portion of said high impurity concentration diffusion region; an oxide layer extending over a portion of said first polycrystalline silicon layer; a resistor comprising a second polycrystalline silicon layer disposed over either one of the gate electrodes of the first and second MOS transistors, one end of said resistor being in direct contact with said first polycrystalline silicon layer through an opening provided over the field oxide layer through said oxide layer, and impurities being thermally diffused from said first polycrystalline silicon layer into that portion of said second polycrystalline silicon layer which is in contact with said first polycrystalline silicon layer, thereby electrically connecting both the first and second polycrystalline silicon layers; and another end portion of said first polycrystalline silicon layer constituting a gate electrode of the gate of said second MOS transistor.