A flash memory including a substrate having a recess, a buried bit line, a word line, a single side insulating layer, a floating gate, a tunneling dielectric layer, a control gate, and an inter-gate dielectric layer is provided. The buried bit line extends below the recess of the substrate along a first direction. The word line is on the substrate, and extends above the recess along a second direction. The single side insulating layer is on a first sidewall of the recess. The floating gate is on a second sidewall of the recess to be opposite to the single side insulating layer. The tunneling dielectric layer is sandwiched by the floating gate and the substrate to contact the buried bit line. The control gate fills the recess and contacts the word line. The inter-gate dielectric layer is sandwiched by the control gate and the floating gate.