A NAND type flash memory for increasing data read/write reliability includes a semiconductor substrate unit, a base unit, and a plurality of data storage units. The semiconductor substrate unit includes a semiconductor substrate. The base unit includes a first dielectric layer formed on the semiconductor substrate. The data storage units are formed on the first dielectric layer. Each data storage unit includes two floating gates formed on the first dielectric layer, two inter-gate dielectric layers respectively formed on the two floating gates, two control gates respectively formed on the two inter-gate dielectric layers, a second dielectric layer formed on the first dielectric layer, between the two floating gates, between the two inter-gate dielectric layers, and between the two control gates, and a third dielectric layer formed on the first dielectric layer and surrounding and connecting with the two floating gates, the two inter-gate dielectric layers, and the two control gates.