Abstract: Semiconductor integrated circuits comprising a dielectric isolation semiconductor chip having a plurality of monocrystalline semiconductor regions electrically separated by a polycrystalline semiconductor and dielectric insulation films, and circuit elements formed in the monocrystalline regions, wherein the polycrystalline substrate includes a high resistivity layer and a low resistivity layer, at least the high resistivity layer is adjacent to the monocrystalline region and the low resistivity region is coupled to a contact provided on a surface of the chip, whereby an electrostatic coupling between the circuit elements is shielded by the low resistivity layer to prevent cross-talks due to the electrostatic coupling. A method of manufacturing the same is also disclosed.

Abstract: A semiconductor integrated circuit device in which circuit elements to constitute one semiconductor integrated circuit device are divided into one group needing the dielectric isolation of the elements from one another and the other group not needing such dielectric isolation, the elements in the one group are isolated from one another in monocrystalline semiconductor regions defined through dielectric isolation in the substrate, the elements in the other group are formed in those parts of monocrystalline semiconductor region defined through dielectric isolation in the substrate which are separated by the impurity doped regions whose conductivity type is opposite to that of the monocrystalline semiconductor region, and the impurity doped region is connected to the most negative or positive potential of a circuit including at least the elements in the other group, whereby the circuit device can have a high integration density and can operate excellently even in high frequency range.

Abstract: A semiconductor bidirectional switch comprising a couple of thyristor pairs connected in parallel in opposite directions, each of the pairs comprising a cathode gate drive thyristor and an anode-gate drive thyristor, is disclosed, in which the cathode-gates of the cathode-gate drive thyristors are connected to a cathode-gate drive circuit for supplying current and the anode-gates of the anode-gate drive thyristors are connected to an anode-gate drive circuit for taking out current, so that the gate current of the thyristors continues to flow without regard to the amplitude of the signal voltage, thereby permitting the AC signal current to flow therethrough without any momentary cut off even when the AC signal current is reduced below the minimum holding current level of the thyristors.

Abstract: A semiconductor speech path switch circuitry is disclosed in which a terminal is provided to one region of a semiconductor device located between two points to be channeled to each other and having a four-region structure of PNPN with three PN junctions, the one region having the lowest impurity concentration in the semiconductor device and also determining the breakdown voltage thereof, a bias voltage being applied to the terminal through a variable impedance circuit exhibiting a high impedance in the turned-on state of the semiconductor device while exhibiting a low impedance in the turned-off state of the semiconductor device. In the semiconductor channel switch circuitry, the crosstalk through the junction capacitances is greatly reduced and the available frequency band is wide.