Disclosed are a design method and structure for a transistor having a relatively large threshold voltage (Vt) variation range due to exacerbated random dopant fluctuation (RDF). Exacerbated RDF and, thereby a relatively large Vt variation range, is achieved through the use of complementary doping in one or more transistor components and/or through lateral dopant non-uniformity between the channel region and any halo regions. Also disclosed are a design method and structure for a random number generator, which incorporates multiple pairs of essentially identical transistors having such a large Vt variation and which relies on Vt mismatch in pairs of those the transistors to generate a multi-bit output (e.g., a unique identifier for a chip or a secret key). By widening the Vt variation range of the transistors in the random number generator, detecting Vt mismatch between transistors becomes more likely and the resulting multi-bit output will be more stable.