1. Introduction

2. Observations and data reduction
2.1. Sample selection
2.2. IRAM Plateau de Bure observations
2.3. Interferometric data reduction

3. Results of the A-configuration PdBI observations
3.2. 12CO(2-1) data

4. Nature of the secondary components detected in the millimeter continuum maps

5. Dust continuum emission detected toward the primary Class 0 sources

6. Discussion: Constraints on the formation of multiple systems
6.2. Comparison with numerical models of binary fragmentation

7. Summary and conclusions