A N-channel MOS random access memory of the one transistor type is disclosed. The cell utilizes an ion implanted area beneath the capacitor dielectric to permit lower bias voltages on the capacitor. In one example, two levels of polycrystalline silicon are used, one for the bias voltage side of the storage capacitor, and the other for the gate of the MOS transistor and to connect the gate to the bit select line. The capacitor dielectric may be formed of thermal SiO.sub.2 which is about half as thick as the gate insulator of the MOS transistor in the cell. In another example, a single-level poly cell uses an implanted region for the same purpose; the capacitor dielectric is the same thickness as the MOS gate insulator so the lower bias voltage functions to reduce stress failures of the dielectric.
This is a division of application Ser. No. 210,164, filed Jun. 21, 1988, now U.S. Pat. No. 4,827,448 which is a continuation, of pending application Ser. No. 552,637, filed Nov. 6, 1984, now abandoned which is a continuation, of application Ser. No. 199,417, filed Oct. 22, 1980, now abandoned which is a divisional, of appliation Ser. No. 722,841, filed Sep. 13, 1976, now U.S. Pat. No. 4,240,092.
A method of fabricating a MOS capacitor in a complementary MOS fabrication process with dual-doped poly gates comprises providing a substrate of a first conductive type, the substrate having a first well of the first conductive type and a second well of a second conductive type. A dielectric layer is formed on the substrate. A first poly gate of the first conductive type is formed on the dielectric layer over the first well and a second poly gate of the second conductive type is formed on the dielectric layer over the second well. A first doped region of the first conductive type is formed in the substrate at each side of the first poly gate. A second doped region of the second conductive type is formed in the substrate at each side of the second poly gate layer. A spacer is formed on sidewalls of the first poly gate and the second poly gate, wherein a portion of the dielectric layer is also removed to expose a portion of the first doped region and a portion of the second doped region. An implantation is performed on the exposed portion of the first doped region with dopants of the first conductive type, so as to form a first substrate electrode. An implantation process is performed on the exposed portion of the second doped region with dopants of the second conductive type to form a second substrate electrode.
A capacitor may be formed by implanting after forming a dielectric and a conductive layer over a semiconductor structure. This diminishes the implant damage to the region underneath the conductive layer. Implanted impurities may be driven under the conductive layer such that two opposed impurity profiles overlap. This forms a junction under the conductive layer.
The present invention provides a polycrystalline silicon conducting structure (e.g., a resistor) whose resistance value is controlled, and can be less variable and less dependent on temperature with respect to any resistant value, and a process of producing the same. Use is made of at least a two-layer structure including a first polycrystalline silicon layer of large crystal grain size and a second polycrystalline silicon layer of small crystal grain size, and the first polycrystalline silicon layer has a positive temperature dependence of resistance while the second polycrystalline layer has a negative temperature dependence of resistance, or vice versa. Moreover, the polycrystalline silicon layer of large grain size can be formed by high dose ion implantation and annealing, or by depositing the layers by chemical vapor deposition at different temperatures so as to form large-grain and small-grain layers.
The present invention provides a polycrystalline silicon conducting structure (e.g., a resistor) whose resistance value is controlled, and can be less variable and less dependent on temperature with respect to any resistant value, and a process of producing the same. Use is made of at least a two-layer structure including a first polycrystalline silicon layer of large crystal grain size and a second polycrystalline silicon layer of small crystal grain size, and the polycrystalline first silicon layer has a positive in temperature dependence of resist while the second polycrystalline layer has a negative temperature dependence of resistance, or vice versa. Moreover, the polycrystalline silicon layer of large grain size can be formed by high dose ion implantation and annealing, or by depositing the layers by chemical vapor deposition at different temperatures so as to form large-grain and small-grain layers.
The present invention provides a polycrystalline silicon conducting structure (e.g., a resistor) whose resistance value is controlled, and can be less variable and less dependent on temperature with respect to any resistant value, and a process of producing the same. Use is made of at least a two-layer structure including a first polycrystalline silicon layer of large crystal grain size and a second polycrystalline silicon layer of small crystal grain size, and the first polycrystalline silicon layer has a positive temperature dependence of resistance while the second polycrystalline silicon layer has a negative temperature dependence of resistance, or vice versa. Moreover, the polycrystalline silicon layer of large grain size can be formed by high dose ion implantation and annealing, or by depositing the layers by chemical vapor deposition at different temperatures so as to form large-grain and small-grain layers.
