Secure digital chips such as those found in smart cards are widely used for financial transactions and the transfer of confidential information. Small circuits for high-level information security have to be implemented in these chips. These secure circuits thus require a small ph-RNG (physical random-number generator) capable of generating unpredictable random numbers. A smart card of just a few mm 2 is almost entirely occupied by the CPU, coprocessor, random logic, ROM, RAM, EEPROM, etc., and the memory capacity required is increasing. However, the circuit area of previous ph-RNGs is large, since there is a complex trade-off among circuit area, quality of random numbers and data generation rate. To solve the tradeoff, we use SiN MOSFET as a noise source device, and design a compact A/D converter for SiN MOS-FET RNG. Together these components form a compact ph-RNG circuit as small as 1200μm 2 with a generation rate of 2Mb/s. This ph-RNG circuit area is smaller than one-third of that of any ph-RNG previously reported [1][2][3][4][5], compared at the same generation rate. Furthermore, the quality of random numbers generated by the SiN MOSFET ph-RNG does not depend on temperature, since the origin of random noise signal is a direct tunneling process, theoretically independent of temperature, whereas the origin of random noise in previous ph-RNG is from thermal processes.Previous ph-RNGs are based on thermal noise or thermal carrier injection/ejection in a single or few local traps [1][2][3][4][5]. These noise signals are very small, especially at high frequency, although large noise signals at high frequency are better for a ph-RNG. We use a MOSFET with high-density electron traps in a SiN layer near a Si channel for a noise source ( Fig. 22.8.1). The SiN layer is formed by the same CVD used in the conventional CMOS mass-production process. The SiN MOSFET is fabricated with a CMOS process and one additional photo mask. Electrons are injected/ejected quickly between the Si channel and local traps in SiN layer by direct tunneling. According to electron injection/ejection in many local traps, a large conductance change in the transistor is seen as a large drain current (I d ) fluctuation in the SiN MOSFET. The noise signal of SiN MOSFET is much larger than that of a conventional MOSFET, as shown in Fig. 22.8.1. The circuit blocks for conventional ph-RNG and the SiN MOSFET one are shown in Fig. 22.8.2. Most conventional ph-RNGs require large amplification of the noise signal or a large array of identical noise generators and A/D converters in order to attain over 1Mb/s generation rate, since the noise signals are very small at high frequency. As a result, the amplifier or A/D converter has been very large. In this work, because of the high-amplitude random noise at high frequency from the SiN MOSFET, we need only a single amplifier and A/D converter, and the amplifier area is decreased, as shown in Fig. 22.8.2.In addition to an amplifier and A/D converter, a RNG also needs filters to cut off low-frequency noise origina...