Scatter File - When i compile, the memory that i dont use i filled with zero - STM32F407

Hi, im writing a Scatter File in Keil where i have a sector only for start that decide between go to the Application and Bootloader:

LR_IROM1 0x08000000 0x00100000 ;load region size_region
{

ER_IROM_RESET 0x08000000 FIXED 0x00020000 ;Sector 0
{

Start.o (RESET_DATA, +FIRST)
Start.o (RESET_CODE, +RO)

}
ER_IROM_PROGRAM 0x08020000 FIXED 0x000E0000
{

*.o (START_DATA_PROG, +FIRST) ;
*(InRoot$$Sections)

.ANY (+RO)
.ANY (+XO)

}
RW_VarShGeneral_Z012 0x20000000 0x00000800 ;2 KBytes
{

SW_gct.o (Seccion_Sh, +RW-DATA)

}
RW_SRAM1 0x20000800 ;RW data (112K)
{

.ANY (+RW +ZI)

}

RW_SRAM2 0x2001C000 0x00004000 ;RW data (16K)

{

.ANY (+RW +ZI)

}

}

My problem is that when compile and load the project, the memory for example in the range [0x08000000, 0x08020000] that i dont use is filled with Zero value. I probe change the size of this sector [0x00020000] to [0x00000200] and it not resolve the problem. Why it fills the sector with 0x00?