Patent ID: 6317305
Filing Date: 2001-11-13
Classification: H01L

Abstract:
A semiconductor device having electrostatic discharge protection for internal circuitry, the device being connected in use to first and second power supply lines, the first power supply line being positive with respect to the second power supply line, the device comprising:a connection terminal for connecting the internal circuitry of the device to external circuitry, the connection-terminal potential being permitted to vary, in use of the device, within a predetermined range of potentials including a potential equal or close to the potential of the second power supply line of the device; andelectrostatic discharge protection circuitry including a P-type field-effect transistor having a source region connected to said connection terminal, a gate connected so as to be equal or close in potential to said source region, and a drain region connected to a discharge path whose potential is such that the transistor turns ON when the connection-terminal potential falls below a predetermined protection potential, and a region of N-type semiconductor material, surrounding said source region, being maintained at a potential such that a source diode, effectively formed between said source region and said surrounding region of said source region when the device is in use, is reverse-biased by at least a predetermined source diode reverse-bias potential for any value of said connection-terminal potential within said predetermined range, thereby to reduce adverse effects of a parasitic capacitance associated with said source diode for connection-terminal potentials within said predetermined range.