A first silicon controlled rectifier has a breakdown voltage in a first direction and a breakdown voltage in a second direction. A second silicon controlled rectifier has a breakdown voltage with a higher magnitude than the first silicon controlled rectifier in the first direction, and a breakdown voltage with a lower magnitude than the first silicon controlled rectifier in the second direction. A bidirectional electrostatic discharge (ESD) structure utilizes both the first silicon controlled rectifier and the second silicon controlled rectifier to provide bidirectional protection.

A two-transistor memory cell based upon a thyristor for an SRAM integrated circuit is described together with a process for fabricating it. The memory cell can be implemented in different combinations of MOS and bipolar select transistors, or without select transistors, with thyristors in a semiconductor substrate with shallow trench isolation. Standard CMOS process technology can be used to manufacture the SRAM.

A silicon-controlled rectifier (SCR) includes a first-type field, a second-type first field and a second-type second field disconnectedly formed in a first-type well; an entire first-type doped region formed within the first-type field; a segmented second-type doped region formed within the second-type first field; and a segmented first-type doped region formed within the second-type second field.

Protection circuits and methods for protecting an integrated circuit against an over-limit electrical condition are provided. One example includes a snapback circuit having at least a portion formed in an isolated doped well region and configured to switch to a low impedance state in response to an input exceeding a trigger condition and further having a control circuit coupled to a reference voltage and further coupled to the isolated doped well region and the portion of the snapback circuit formed in the doped well region. The control circuit includes an impedance adjustable in response to a control signal and configured to adjust an isolated doped well impedance in which at least a portion of the snapback circuit is formed relative to the reference voltage. A modulated trigger and hold condition tot the snapback circuit can be set according to a control signal adjusting an electrical impedance of the control circuit.

A silicon controlled rectifier, an electrostatic discharge (ESD) protection circuit including the silicon controlled rectifier and an integrated circuit including the silicon controlled rectifier or ESD protection circuit. The silicon controlled rectifier includes a first region having a first conductivity type and a second region having a second conductivity type located adjacent the first region in a semiconductor substrate. A junction is formed at a boundary between the first region and the second region. Contact regions of the first conductivity type and the second conductivity type located in each of the first region and the second region. A further contact region of the second conductivity type is located in the second region, in between the contact region of the first conductivity type and the junction. The further contact region and the contact region of the second conductivity type in the second region are connected together for biasing the second region.

An ESD protection semiconductor device includes a substrate, a buried layer buried in the substrate, a first well formed in the substrate, a first doped region formed in the first well, a second doped region formed in the first well and adjacent to the first doped region, a second well formed in the first well, and a third doped region formed in the second well. The buried layer, the first well, the first doped region, and the third doped region include a first conductivity type while the second doped region and the second well include a second conductivity type complementary to the first conductivity type. The second well is spaced apart from the first doped region and the second doped region by the first well.

A semiconductor device is provided which comprises an ESD protection device. The structure of the semiconductor device comprises a p-doped isolated region in which a structure is manufactured which operates as a Silicon Controlled Rectifier which is coupled between an I/O pad and a reference voltage or ground voltage. The semiconductor device also comprises a pnp transistor which is coupled parallel to the Silicon Controlled Rectifier. The base of the transistor is coupled to the gate of the Silicon Controlled Rectifier. In an optional embodiment, the base and gate are also coupled to the I/O pad.

An electro-static discharge (ESD) protection device includes a first PN diode, a second PN diode and a silicon controlled rectifier (SCR). The first PN diode and the second PN diode are coupled in series between a pad and a ground voltage to provide a first discharge current path. The SCR is coupled between the pad and the ground voltage to provide a second discharge current path. The SCR has a PNPN structure.

Disclosed is an electrostatic discharge (ESD) protection circuit. The ESD protection circuit may include a silicon controller rectifier (SCR) which may be triggered via at least one of its first trigger gate or second trigger gate. The ESD protection circuit may further include a highly doped region coupled to either the anode or cathode of the SCR, wherein the highly doped region may provide additional carriers to facilitate triggering of the SCR during an ESD event, whereby the SCR may be triggered more quickly.

An electrostatic discharge protection device includes: a substrate of a second conductivity type, the substrate including a well of a first conductivity type; a cathode electrode connected to the substrate; a first diffusion region of the second conductivity type and a second diffusion region of the first conductivity type, formed in the substrate and connected to the cathode electrode; an anode electrode connected to the substrate; a third diffusion region of the second conductivity type and a fourth diffusion region of the first conductivity type, formed in the well and connected to the anode electrode; a fifth diffusion region of the first conductivity type, formed on a border of the substrate and the well; and a sixth diffusion region of the first conductivity type, formed in the substrate between the first and second diffusion regions and the fifth diffusion region and configured to receive a bias voltage from outside.