Integrated circuits with asymmetric transistors

摘要

Integrated circuits with memory elements are provided. A memory element may include a storage circuit coupled to data lines through access transistors. Access transistors may be used to read data from and write data into the storage circuit. An access transistor may have asymmetric source-drain resistances. The access transistor may have a first source-drain that is coupled to a data line and a second source-drain that is coupled to the storage circuit. The second source-drain may have a contact resistance that is greater than the contact resistance associated with the first source-drain. Access transistors with asymmetric source-drain resistances may have a first drive strength when passing a low signal and a second drive strength when passing a high signal to the storage circuit. The second drive strength may be less than the first drive strength. Access transistors with asymmetric drive strengths may be used to improve memory read/write performance.

主权项

1. An asymmetric transistor comprising:
a gate conductor; a first source-drain region formed in a semiconductor substrate; a second source-drain region formed in the semiconductor substrate; a channel region under the gate conductor that is interposed between the first and second source-drain regions; a first stress-inducing layer that applies a first stress to a portion of the channel region that is adjacent to the first source-drain region; and a second stress-inducing layer that applies a second stress that is different than the first stress to a portion of the channel region that is adjacent to the second source-drain region.