Single electron transistors (SET) are indispensible devices for quantum information processing and our Si based SETs have several advantages like high integration densities, low cost, and long spin decoherence time. We will further develop the technologies towards the practical implementation to the industry by optimising the fabrication process technologies in Southampton Nanofabrication Centre and examining them in the world leading low temperature measurement facilities. Especially, we will develop Si based SETs defined by the atomically flat interfaces to achieve the robust design capabilities against the interfacial defects and surface roughness, which are important for scalabilities and mass production.