Semiconductor device and method for production thereof

A semiconductor device comprising:

• a semiconductor substrate having regions with a high impurity concentration selectively located therein,
• a first insulator layer formed on said substrate to selectively cover said regions of said substrate,
• a highly doped first polycrystalline semiconductor layer formed selectively on said first insulator layer,
• a second insulator layer selectively covering said first polycrystalline semiconductor layer, and
• a second polycrystalline semiconductor layer selectively covering said first and second insulator layers, and selectively contacting parts of the first polycrystalline semiconductor layer and of said substrate regions, at least one of said parts of the first polycrystalline semiconductor layer being located contiguously to at least one of said substrate regions,
• wherein said second polycrystalline semiconductor layer is more heavily doped where it is in contact with said substrate regions and said first polycrystalline semiconductor layer, due to upward diffusion of impurites from said substrate regions and said first polycrystalline semiconductor layer, and
• wherein said first polycrystalline semiconductor layer comprises electrodes and wirings, and said second polycrystalline semiconductor layer comprises resistor elements overlying at least in part said substrate regions.