Digital circuits having improved transistors, and methods therefor
Digital circuits are disclosed that may include multiple transistors having controllable current paths coupled between first and second logic nodes. One or more of the transistors may have a deeply depleted channel formed below its gate that includes a substantially undoped channel region formed over a relatively highly doped screen layer formed over a doped body region. Resulting reductions in threshold voltage variation may improve digital circuit performance. Logic circuit, static random access memory (SRAM) cell, and passgate embodiments are disclosed.
1. A logic circuit coupled to receive a plurality of input signals, comprising:
a plurality of transistors having controllable current paths coupled between a first logic node and a second logic node, the transistors configured to selectively couple an output node to the first or second logic node in response to at least one input signal, at least one transistor having a gate with a gate oxide atop a substantially undoped channel region formed over a relatively highly doped screen layer formed over a doped body region, the at least one transistor having a sufficiently strong body coefficient so that a bias voltage can be effectively applied to the body of the at least one transistor, the highly doped screen layer defining a depletion depth when a voltage is applied to the gate;
wherein pairs of said plurality of transistors are of complementary conductivity types, each transistor of a pair having a gate having a selected work function; and
wherein said logic circuit comprises a digital logic functionality.
2. The circuit of claim 1 , wherein:
the plurality of transistors are configured to generate an output signal that is a logical function of, and timed in response to, the at least one input signal.
3. The circuit of claim 1 , wherein the digital logic functionality comprises a NOT function, an AND function, an OR function, a NAND function, and a NOR function.
4. The circuit of claim 1 , wherein the digital logic functionality comprises a flip flop.
5. The circuit of claim 1 , wherein said digital logic functionality comprises a latch.